Christine M. Lohse, MS

The incidence of cutaneous melanoma in the United States has increased in the last 30 years, with the American Cancer Society estimating that 99,780 new melanomas will be diagnosed and 7650 melanoma-related deaths will occur in 2022.¹ Patients with melanoma have an increased risk for developing a second primary melanoma or other malignancy, such as salivary gland, small intestine, breast, prostate, renal, or thyroid cancer, but most commonly nonmelanoma skin cancer.^2,3 The incidence rate of melanoma among residents of Olmsted County, Minnesota, from 1970 through 2009 has already been described for various age groups^4-7; however, the incidence of a second primary malignancy, including melanoma, within these incident cohorts remains unknown.

Mutations in the BRAF oncogene occur in approximately 50% of melanomas.^8,9They cause downstream activation of the mitogen-activated protein kinase signaling pathway, stimulating growth in melanoma cell lines.¹⁰BRAF mutations also occur in hairy cell leukemia, papillary thyroid cancers, colorectal cancers, liver cancers, gliomas, lung cancers, sarcomas, ovarian cancers, and breast cancers, with incidence rates varying from 2% to 100%.^9,11,12 V600E is the most common somatic BRAF mutation (>90%) and is linked to survival in melanoma.¹³ Targeted therapies with small-molecule BRAF and MEK inhibitors have notably improved survival of patients with advanced or metastatic disease,¹⁴ and molecular testing for BRAF mutations is routinely recommended for patients with advanced melanoma.

Although the BRAF mutation event in melanoma is sporadic and should not necessarily affect the development of an unrelated malignancy, we hypothesized that the exposures that may have predisposed a particular individual to a BRAF-mutated melanoma also may have a higher chance of predisposing that individual to the development of another primary malignancy. In this population-based study, we aimed to determine whether the specific melanoma feature of mutant BRAF V600E expression was associated with the development of a second primary malignancy.

Methods

This study was approved by the institutional review boards of the Mayo Clinic and Olmsted Medical Center (both in Rochester, Minnesota). The reporting of this study is compliant with the Strengthening the Reporting of Observational Studies in Epidemiology statement.¹⁵

Patient Selection and BRAF Assessment—The Rochester Epidemiology Project (REP) links comprehensive health care records for virtually all residents of Olmsted County, Minnesota, across different medical providers. The REP provides an index of diagnostic and therapeutic procedures, tracks timelines and outcomes of individuals and their medical conditions, and is ideal for population-based studies. Since its inception in 1966, the REP has provided the resource for more than 2000 peer-reviewed publications.^16,17

We obtained a list of all residents of Olmsted County aged 18 to 60 years who had a melanoma diagnosed according to the International Classification of Diseases, Ninth Revision, from January 1, 1970, through December 30, 2009; these cohorts have been analyzed previously.^4-7 Of the 638 individuals identified, 380 had a melanoma tissue block on file at Mayo Clinic with enough tumor present in available tissue blocks for BRAF assessment. All specimens were reviewed by a board-certified dermatopathologist (J.S.L.) to confirm the diagnosis of melanoma. Tissue blocks were recut, and formalin-fixed, paraffin-embedded tissue sections were stained for BRAF V600E (Spring Bioscience Corporation). BRAF-stained specimens and the associated hematoxylin and eosin−stained slides were reviewed. Melanocyte cytoplasmic staining for BRAF was graded as negative if no staining was evident. BRAF was graded as positive if focal or partial staining was observed (<50% of tumor or low BRAF expression) or if diffuse staining was evident (>50% of tumor or high BRAF expression).

Using resources of the REP, we confirmed patients’ residency status in Olmsted County at the time of diagnosis of the incident melanoma. Patients who denied access to their medical records for research purposes were excluded. We used the complete record of each patient to confirm the date of diagnosis of the incident melanoma. Baseline characteristics of patients and their incident melanomas (eg, anatomic site and pathologic stage according to the American Joint Committee on Cancer classification) were obtained. When only the Clark level was included in the dermatopathology report, the corresponding Breslow thickness was extrapolated from the Clark level,¹⁸ and the pathologic stage according to the American Joint Committee on Cancer classification (7th edition) was determined.

For our study, specific diagnostic codes—International Classification of Diseases, Ninth and Tenth Revisions; Hospital International Classification of Diseases Adaptation¹⁹; and Berkson¹⁶—were applied across individual records to identify all second primary malignancies using the resources of the REP. The diagnosis date, morphology, and anatomic location of second primary malignancies were confirmed from examination of the clinical records. For squamous cell carcinomas and basal cell carcinomas (BCCs), of which multiple tumors could potentially occur in a single patient, the dates of the earliest squamous cell carcinomas and BCCs that occurred before and after the incident melanoma were used. For second primary malignancies, the biopsy date was used as the diagnosis date, except for a few patients who presented with such advanced-stage cancer that the diagnosis was ascertained by clinical examination and radiologic imaging alone.

Statistical Analysis—Baseline characteristics were compared by BRAF V600E expression using Wilcoxon rank sum and χ² tests. The rate of developing a second primary malignancy at 5, 10, 15, and 20 years after the incident malignant melanoma was estimated with the Kaplan-Meier method. The duration of follow-up was calculated from the incident melanoma date to the second primary malignancy date or the last follow-up date. Patients with a history of the malignancy of interest, except skin cancers, before the incident melanoma date were excluded because it was not possible to distinguish between recurrence of a prior malignancy and a second primary malignancy. Associations of BRAF V600E expression with the development of a second primary malignancy were evaluated with Cox proportional hazards regression models and summarized with hazard ratios (HRs) and 95% CIs; all associations were adjusted for potential confounders such as age at the incident melanoma, year of the incident melanoma, and sex.

Results

Demographics—Table 1 shows the demographic and melanoma-specific characteristics of the 380 patients evaluated for mutant BRAF V600E expression. At last follow-up, 48 patients had died at a median (interquartile range [IQR]) of 6.7 (1.7–14.0) years after the incident melanoma. The median (IQR) duration of follow-up for the 332 living patients was 11.8 (9.1–18.3) years. Three hundred seventy-eight (99%) patients were White. One hundred thirty-three (35%) and 247 (65%) patients were confirmed to have BRAF V600E–positive and BRAF V600E–negative melanomas, respectively.

Cumulative Incidence of Second Primary Melanoma—Of 133 patients with positive BRAF V600E expression, we identified 14 (10.5%), 1 (0.8%), and 1 (0.8%) who had 1, 2, and 4 subsequent melanomas, respectively. Of the 247 patients with negative BRAF V600E expression, we identified 15 (6%), 4 (1.6%), 2 (0.8%), and 1 (0.4%) patients who had 1, 2, 3, and 4 subsequent melanomas, respectively; BRAF V600E expression was not associated with the number of subsequent melanomas (P=.37; Wilcoxon rank sum test). The cumulative incidences of developing a second primary melanoma (n=38 among the 380 patients studied) at 5, 10, 15, and 20 years after the incident melanoma were 5.3%, 7.6%, 8.1%, and 14.6%, respectively.

Cumulative Incidence of All Second Primary Malignancies—Of the 380 patients studied, 60 (16%) had at least 1 malignancy diagnosed before the incident melanoma. Of the remaining 320 patients, 104 later had at least 1 malignancy develop, including a second primary melanoma, at a median (IQR) of 8.0 (2.7–16.2) years after the incident melanoma; the 104 patients with at least 1 subsequent malignancy included 40 with BRAF-positive and 64 with BRAF-negative melanomas. The cumulative incidences of developing at least 1 malignancy of any kind at 5, 10, 15, and 20 years after the incident melanoma were 15.0%, 20.5%, 31.2%, and 47.0%, respectively. Table 2 shows the number of patients with at least 1 second primary malignancy after the incident melanoma stratified by BRAF status.

BRAF V600E Expression and Association With Second Primary Malignancy—The eTable shows the associations of mutant BRAF V600E expression status with the development of a new primary malignancy. Malignancies affecting fewer than 10 patients were excluded from the analysis because there were too few events to support the Cox model. Positive BRAF V600E expression was associated with subsequent development of BCCs (HR, 2.32; 95% CI, 1.35-3.99; P=.002) and the development of all combined second primary malignancies excluding melanoma (HR, 1.65; 95% CI, 1.06-2.56; P=.03). However, BRAF V600E status was no longer a significant factor when all second primary malignancies, including second melanomas, were considered (P=.06). Table 3 shows the 5-, 10-, 15-, and 20-year cumulative incidences of all second primary malignancies according to mutant BRAF status.

Comment

Association of BRAF V600E Expression With Second Primary Malignancies—BRAF V600E expression of an incident melanoma was associated with the development of all combined second primary malignancies excluding melanoma; however, this association was not statistically significant when second primary melanomas were included. A possible explanation is that individuals with more than 1 primary melanoma possess additional genetic risk—CDKN2A or CDKN4 gene mutations or MC1R variation—that outweighed the effect of BRAF expression in the statistical analysis.

The 5- and 10-year cumulative incidences of all second primary malignancies excluding second primary melanoma were similar between BRAF-positive and BRAF-negative melanoma, but the 15- and 20-year cumulative incidences were greater for the BRAF-positive cohort. This could reflect the association of BRAF expression with BCCs and the increased likelihood of their occurrence with cumulative sun exposure and advancing age. BRAF expression was associated with the development of BCCs, but the reason for this association was unclear. BRAF-mutated melanoma occurs more frequently on sun-protected sites,²⁰ whereas sporadic BCC generally occurs on sun-exposed sites. However, BRAF-mutated melanoma is associated with high levels of ambient UV exposure early in life, particularly birth through 20 years of age,²¹ and we speculate that such early UV exposure influences the later development of BCCs. The lack of an association between BRAF positivity and the development of other specific cancers is possibly because the mutation is somatic and not inherited or germline, as with the CDKN2A mutation, and/or because of the small size of our cohorts.

Development of BRAF-Mutated Cancers—It currently is not understood why the same somatic mutation can cause different types of cancer. A recent translational research study showed that in mice models, precursor cells of the pancreas and bile duct responded differently when exposed to PIK3CA and KRAS oncogenes, and tumorigenesis is influenced by specific cooperating genetic events in the tissue microenvironment. Future research investigating these molecular interactions may lead to better understanding of cancer pathogenesis and direct the design of new targeted therapies.^22,23

Regarding environmental influences on the development of BRAF-mutated cancers, we found 1 population-based study that identified an association between high iodine content of drinking water and the prevalence of T1799A BRAF papillary thyroid carcinoma in 5 regions in China.²⁴ Another study identified an increased risk for colorectal cancer and nonmelanoma skin cancer in the first-degree relatives of index patients with BRAF V600E colorectal cancer.²⁵ Two studies by institutions in China and Sweden reported the frequency of BRAF mutations in cohorts of patients with melanoma.^26,27

Additional studies investigating a possible association between BRAF-mutated melanoma and other cancers with larger numbers of participants than in our study may become more feasible in the future with increased routine genetic testing of biopsied cancers.

Study Limitations—Limitations of this retrospective epidemiologic study include the possibility of ascertainment bias during data collection. We did not account for known risk factors for cancer (eg, excessive sun exposure, smoking). The Olmsted County population is mostly White, and residents have relatively easy access to health care; these factors should be considered when generalizing the results to other populations. Basal cell carcinomas are common skin cancers, and there may be other risk factors influencing the development of BCCs in our cohort. BRAF mutation analysis was available in only a small number of patients (n=380; aged 18–60 years), which would have reduced our capacity to identify statistically significant associations. A positive BRAF result did not differentiate between high and low expression levels, but expression levels may affect patient outcomes. One study showed that high BRAF expression correlated with significantly poorer overall (P=.009) and disease-specific 5-year survival (P=.007) for 232 patients with primary melanoma.²⁸

The main clinical implications from this study are that we do not have enough evidence to recommend BRAF testing for all incident melanomas, and BRAF-mutated melanomas cannot be associated with increased risk for developing other forms of cancer, with the possible exception of BCCs. Future research should assess BRAF mutation status of any second primary malignancies that arise after an incident BRAF-positive melanoma.

Conclusion

Physicians should be aware of the risk for a second primary malignancy after an incident melanoma, and we emphasize the importance of long-term cancer surveillance. The association between BRAF expression in incident melanomas and a higher rate of BCC development may provide indirect evidence that high levels of UV light exposure in early life can increase the risk for BCCs later. Although BRAF mutations occur in several nonmelanoma cancers, further studies are needed to determine whether BRAF tissue expression in melanoma affects the development of other cancers.

Acknowledgment—We thank Ms. Jayne H. Feind (Rochester, Minnesota) for assistance with study coordination.

The incidence of cutaneous melanoma in the United States has increased in the last 30 years, with the American Cancer Society estimating that 99,780 new melanomas will be diagnosed and 7650 melanoma-related deaths will occur in 2022.¹ Patients with melanoma have an increased risk for developing a second primary melanoma or other malignancy, such as salivary gland, small intestine, breast, prostate, renal, or thyroid cancer, but most commonly nonmelanoma skin cancer.^2,3 The incidence rate of melanoma among residents of Olmsted County, Minnesota, from 1970 through 2009 has already been described for various age groups^4-7; however, the incidence of a second primary malignancy, including melanoma, within these incident cohorts remains unknown.

Mutations in the BRAF oncogene occur in approximately 50% of melanomas.^8,9They cause downstream activation of the mitogen-activated protein kinase signaling pathway, stimulating growth in melanoma cell lines.¹⁰BRAF mutations also occur in hairy cell leukemia, papillary thyroid cancers, colorectal cancers, liver cancers, gliomas, lung cancers, sarcomas, ovarian cancers, and breast cancers, with incidence rates varying from 2% to 100%.^9,11,12 V600E is the most common somatic BRAF mutation (>90%) and is linked to survival in melanoma.¹³ Targeted therapies with small-molecule BRAF and MEK inhibitors have notably improved survival of patients with advanced or metastatic disease,¹⁴ and molecular testing for BRAF mutations is routinely recommended for patients with advanced melanoma.

Although the BRAF mutation event in melanoma is sporadic and should not necessarily affect the development of an unrelated malignancy, we hypothesized that the exposures that may have predisposed a particular individual to a BRAF-mutated melanoma also may have a higher chance of predisposing that individual to the development of another primary malignancy. In this population-based study, we aimed to determine whether the specific melanoma feature of mutant BRAF V600E expression was associated with the development of a second primary malignancy.

Methods

This study was approved by the institutional review boards of the Mayo Clinic and Olmsted Medical Center (both in Rochester, Minnesota). The reporting of this study is compliant with the Strengthening the Reporting of Observational Studies in Epidemiology statement.¹⁵

Patient Selection and BRAF Assessment—The Rochester Epidemiology Project (REP) links comprehensive health care records for virtually all residents of Olmsted County, Minnesota, across different medical providers. The REP provides an index of diagnostic and therapeutic procedures, tracks timelines and outcomes of individuals and their medical conditions, and is ideal for population-based studies. Since its inception in 1966, the REP has provided the resource for more than 2000 peer-reviewed publications.^16,17

We obtained a list of all residents of Olmsted County aged 18 to 60 years who had a melanoma diagnosed according to the International Classification of Diseases, Ninth Revision, from January 1, 1970, through December 30, 2009; these cohorts have been analyzed previously.^4-7 Of the 638 individuals identified, 380 had a melanoma tissue block on file at Mayo Clinic with enough tumor present in available tissue blocks for BRAF assessment. All specimens were reviewed by a board-certified dermatopathologist (J.S.L.) to confirm the diagnosis of melanoma. Tissue blocks were recut, and formalin-fixed, paraffin-embedded tissue sections were stained for BRAF V600E (Spring Bioscience Corporation). BRAF-stained specimens and the associated hematoxylin and eosin−stained slides were reviewed. Melanocyte cytoplasmic staining for BRAF was graded as negative if no staining was evident. BRAF was graded as positive if focal or partial staining was observed (<50% of tumor or low BRAF expression) or if diffuse staining was evident (>50% of tumor or high BRAF expression).

Using resources of the REP, we confirmed patients’ residency status in Olmsted County at the time of diagnosis of the incident melanoma. Patients who denied access to their medical records for research purposes were excluded. We used the complete record of each patient to confirm the date of diagnosis of the incident melanoma. Baseline characteristics of patients and their incident melanomas (eg, anatomic site and pathologic stage according to the American Joint Committee on Cancer classification) were obtained. When only the Clark level was included in the dermatopathology report, the corresponding Breslow thickness was extrapolated from the Clark level,¹⁸ and the pathologic stage according to the American Joint Committee on Cancer classification (7th edition) was determined.

For our study, specific diagnostic codes—International Classification of Diseases, Ninth and Tenth Revisions; Hospital International Classification of Diseases Adaptation¹⁹; and Berkson¹⁶—were applied across individual records to identify all second primary malignancies using the resources of the REP. The diagnosis date, morphology, and anatomic location of second primary malignancies were confirmed from examination of the clinical records. For squamous cell carcinomas and basal cell carcinomas (BCCs), of which multiple tumors could potentially occur in a single patient, the dates of the earliest squamous cell carcinomas and BCCs that occurred before and after the incident melanoma were used. For second primary malignancies, the biopsy date was used as the diagnosis date, except for a few patients who presented with such advanced-stage cancer that the diagnosis was ascertained by clinical examination and radiologic imaging alone.

Statistical Analysis—Baseline characteristics were compared by BRAF V600E expression using Wilcoxon rank sum and χ² tests. The rate of developing a second primary malignancy at 5, 10, 15, and 20 years after the incident malignant melanoma was estimated with the Kaplan-Meier method. The duration of follow-up was calculated from the incident melanoma date to the second primary malignancy date or the last follow-up date. Patients with a history of the malignancy of interest, except skin cancers, before the incident melanoma date were excluded because it was not possible to distinguish between recurrence of a prior malignancy and a second primary malignancy. Associations of BRAF V600E expression with the development of a second primary malignancy were evaluated with Cox proportional hazards regression models and summarized with hazard ratios (HRs) and 95% CIs; all associations were adjusted for potential confounders such as age at the incident melanoma, year of the incident melanoma, and sex.

Results

Demographics—Table 1 shows the demographic and melanoma-specific characteristics of the 380 patients evaluated for mutant BRAF V600E expression. At last follow-up, 48 patients had died at a median (interquartile range [IQR]) of 6.7 (1.7–14.0) years after the incident melanoma. The median (IQR) duration of follow-up for the 332 living patients was 11.8 (9.1–18.3) years. Three hundred seventy-eight (99%) patients were White. One hundred thirty-three (35%) and 247 (65%) patients were confirmed to have BRAF V600E–positive and BRAF V600E–negative melanomas, respectively.

Cumulative Incidence of Second Primary Melanoma—Of 133 patients with positive BRAF V600E expression, we identified 14 (10.5%), 1 (0.8%), and 1 (0.8%) who had 1, 2, and 4 subsequent melanomas, respectively. Of the 247 patients with negative BRAF V600E expression, we identified 15 (6%), 4 (1.6%), 2 (0.8%), and 1 (0.4%) patients who had 1, 2, 3, and 4 subsequent melanomas, respectively; BRAF V600E expression was not associated with the number of subsequent melanomas (P=.37; Wilcoxon rank sum test). The cumulative incidences of developing a second primary melanoma (n=38 among the 380 patients studied) at 5, 10, 15, and 20 years after the incident melanoma were 5.3%, 7.6%, 8.1%, and 14.6%, respectively.

Cumulative Incidence of All Second Primary Malignancies—Of the 380 patients studied, 60 (16%) had at least 1 malignancy diagnosed before the incident melanoma. Of the remaining 320 patients, 104 later had at least 1 malignancy develop, including a second primary melanoma, at a median (IQR) of 8.0 (2.7–16.2) years after the incident melanoma; the 104 patients with at least 1 subsequent malignancy included 40 with BRAF-positive and 64 with BRAF-negative melanomas. The cumulative incidences of developing at least 1 malignancy of any kind at 5, 10, 15, and 20 years after the incident melanoma were 15.0%, 20.5%, 31.2%, and 47.0%, respectively. Table 2 shows the number of patients with at least 1 second primary malignancy after the incident melanoma stratified by BRAF status.

BRAF V600E Expression and Association With Second Primary Malignancy—The eTable shows the associations of mutant BRAF V600E expression status with the development of a new primary malignancy. Malignancies affecting fewer than 10 patients were excluded from the analysis because there were too few events to support the Cox model. Positive BRAF V600E expression was associated with subsequent development of BCCs (HR, 2.32; 95% CI, 1.35-3.99; P=.002) and the development of all combined second primary malignancies excluding melanoma (HR, 1.65; 95% CI, 1.06-2.56; P=.03). However, BRAF V600E status was no longer a significant factor when all second primary malignancies, including second melanomas, were considered (P=.06). Table 3 shows the 5-, 10-, 15-, and 20-year cumulative incidences of all second primary malignancies according to mutant BRAF status.

Comment

Association of BRAF V600E Expression With Second Primary Malignancies—BRAF V600E expression of an incident melanoma was associated with the development of all combined second primary malignancies excluding melanoma; however, this association was not statistically significant when second primary melanomas were included. A possible explanation is that individuals with more than 1 primary melanoma possess additional genetic risk—CDKN2A or CDKN4 gene mutations or MC1R variation—that outweighed the effect of BRAF expression in the statistical analysis.

The 5- and 10-year cumulative incidences of all second primary malignancies excluding second primary melanoma were similar between BRAF-positive and BRAF-negative melanoma, but the 15- and 20-year cumulative incidences were greater for the BRAF-positive cohort. This could reflect the association of BRAF expression with BCCs and the increased likelihood of their occurrence with cumulative sun exposure and advancing age. BRAF expression was associated with the development of BCCs, but the reason for this association was unclear. BRAF-mutated melanoma occurs more frequently on sun-protected sites,²⁰ whereas sporadic BCC generally occurs on sun-exposed sites. However, BRAF-mutated melanoma is associated with high levels of ambient UV exposure early in life, particularly birth through 20 years of age,²¹ and we speculate that such early UV exposure influences the later development of BCCs. The lack of an association between BRAF positivity and the development of other specific cancers is possibly because the mutation is somatic and not inherited or germline, as with the CDKN2A mutation, and/or because of the small size of our cohorts.

Development of BRAF-Mutated Cancers—It currently is not understood why the same somatic mutation can cause different types of cancer. A recent translational research study showed that in mice models, precursor cells of the pancreas and bile duct responded differently when exposed to PIK3CA and KRAS oncogenes, and tumorigenesis is influenced by specific cooperating genetic events in the tissue microenvironment. Future research investigating these molecular interactions may lead to better understanding of cancer pathogenesis and direct the design of new targeted therapies.^22,23

Regarding environmental influences on the development of BRAF-mutated cancers, we found 1 population-based study that identified an association between high iodine content of drinking water and the prevalence of T1799A BRAF papillary thyroid carcinoma in 5 regions in China.²⁴ Another study identified an increased risk for colorectal cancer and nonmelanoma skin cancer in the first-degree relatives of index patients with BRAF V600E colorectal cancer.²⁵ Two studies by institutions in China and Sweden reported the frequency of BRAF mutations in cohorts of patients with melanoma.^26,27

Additional studies investigating a possible association between BRAF-mutated melanoma and other cancers with larger numbers of participants than in our study may become more feasible in the future with increased routine genetic testing of biopsied cancers.

Study Limitations—Limitations of this retrospective epidemiologic study include the possibility of ascertainment bias during data collection. We did not account for known risk factors for cancer (eg, excessive sun exposure, smoking). The Olmsted County population is mostly White, and residents have relatively easy access to health care; these factors should be considered when generalizing the results to other populations. Basal cell carcinomas are common skin cancers, and there may be other risk factors influencing the development of BCCs in our cohort. BRAF mutation analysis was available in only a small number of patients (n=380; aged 18–60 years), which would have reduced our capacity to identify statistically significant associations. A positive BRAF result did not differentiate between high and low expression levels, but expression levels may affect patient outcomes. One study showed that high BRAF expression correlated with significantly poorer overall (P=.009) and disease-specific 5-year survival (P=.007) for 232 patients with primary melanoma.²⁸

The main clinical implications from this study are that we do not have enough evidence to recommend BRAF testing for all incident melanomas, and BRAF-mutated melanomas cannot be associated with increased risk for developing other forms of cancer, with the possible exception of BCCs. Future research should assess BRAF mutation status of any second primary malignancies that arise after an incident BRAF-positive melanoma.

Conclusion

Physicians should be aware of the risk for a second primary malignancy after an incident melanoma, and we emphasize the importance of long-term cancer surveillance. The association between BRAF expression in incident melanomas and a higher rate of BCC development may provide indirect evidence that high levels of UV light exposure in early life can increase the risk for BCCs later. Although BRAF mutations occur in several nonmelanoma cancers, further studies are needed to determine whether BRAF tissue expression in melanoma affects the development of other cancers.

Acknowledgment—We thank Ms. Jayne H. Feind (Rochester, Minnesota) for assistance with study coordination.

The incidence of cutaneous melanoma in the United States has increased in the last 30 years, with the American Cancer Society estimating that 99,780 new melanomas will be diagnosed and 7650 melanoma-related deaths will occur in 2022.¹ Patients with melanoma have an increased risk for developing a second primary melanoma or other malignancy, such as salivary gland, small intestine, breast, prostate, renal, or thyroid cancer, but most commonly nonmelanoma skin cancer.^2,3 The incidence rate of melanoma among residents of Olmsted County, Minnesota, from 1970 through 2009 has already been described for various age groups^4-7; however, the incidence of a second primary malignancy, including melanoma, within these incident cohorts remains unknown.

Mutations in the BRAF oncogene occur in approximately 50% of melanomas.^8,9They cause downstream activation of the mitogen-activated protein kinase signaling pathway, stimulating growth in melanoma cell lines.¹⁰BRAF mutations also occur in hairy cell leukemia, papillary thyroid cancers, colorectal cancers, liver cancers, gliomas, lung cancers, sarcomas, ovarian cancers, and breast cancers, with incidence rates varying from 2% to 100%.^9,11,12 V600E is the most common somatic BRAF mutation (>90%) and is linked to survival in melanoma.¹³ Targeted therapies with small-molecule BRAF and MEK inhibitors have notably improved survival of patients with advanced or metastatic disease,¹⁴ and molecular testing for BRAF mutations is routinely recommended for patients with advanced melanoma.

Although the BRAF mutation event in melanoma is sporadic and should not necessarily affect the development of an unrelated malignancy, we hypothesized that the exposures that may have predisposed a particular individual to a BRAF-mutated melanoma also may have a higher chance of predisposing that individual to the development of another primary malignancy. In this population-based study, we aimed to determine whether the specific melanoma feature of mutant BRAF V600E expression was associated with the development of a second primary malignancy.

Methods

This study was approved by the institutional review boards of the Mayo Clinic and Olmsted Medical Center (both in Rochester, Minnesota). The reporting of this study is compliant with the Strengthening the Reporting of Observational Studies in Epidemiology statement.¹⁵

Patient Selection and BRAF Assessment—The Rochester Epidemiology Project (REP) links comprehensive health care records for virtually all residents of Olmsted County, Minnesota, across different medical providers. The REP provides an index of diagnostic and therapeutic procedures, tracks timelines and outcomes of individuals and their medical conditions, and is ideal for population-based studies. Since its inception in 1966, the REP has provided the resource for more than 2000 peer-reviewed publications.^16,17

We obtained a list of all residents of Olmsted County aged 18 to 60 years who had a melanoma diagnosed according to the International Classification of Diseases, Ninth Revision, from January 1, 1970, through December 30, 2009; these cohorts have been analyzed previously.^4-7 Of the 638 individuals identified, 380 had a melanoma tissue block on file at Mayo Clinic with enough tumor present in available tissue blocks for BRAF assessment. All specimens were reviewed by a board-certified dermatopathologist (J.S.L.) to confirm the diagnosis of melanoma. Tissue blocks were recut, and formalin-fixed, paraffin-embedded tissue sections were stained for BRAF V600E (Spring Bioscience Corporation). BRAF-stained specimens and the associated hematoxylin and eosin−stained slides were reviewed. Melanocyte cytoplasmic staining for BRAF was graded as negative if no staining was evident. BRAF was graded as positive if focal or partial staining was observed (<50% of tumor or low BRAF expression) or if diffuse staining was evident (>50% of tumor or high BRAF expression).

Using resources of the REP, we confirmed patients’ residency status in Olmsted County at the time of diagnosis of the incident melanoma. Patients who denied access to their medical records for research purposes were excluded. We used the complete record of each patient to confirm the date of diagnosis of the incident melanoma. Baseline characteristics of patients and their incident melanomas (eg, anatomic site and pathologic stage according to the American Joint Committee on Cancer classification) were obtained. When only the Clark level was included in the dermatopathology report, the corresponding Breslow thickness was extrapolated from the Clark level,¹⁸ and the pathologic stage according to the American Joint Committee on Cancer classification (7th edition) was determined.

For our study, specific diagnostic codes—International Classification of Diseases, Ninth and Tenth Revisions; Hospital International Classification of Diseases Adaptation¹⁹; and Berkson¹⁶—were applied across individual records to identify all second primary malignancies using the resources of the REP. The diagnosis date, morphology, and anatomic location of second primary malignancies were confirmed from examination of the clinical records. For squamous cell carcinomas and basal cell carcinomas (BCCs), of which multiple tumors could potentially occur in a single patient, the dates of the earliest squamous cell carcinomas and BCCs that occurred before and after the incident melanoma were used. For second primary malignancies, the biopsy date was used as the diagnosis date, except for a few patients who presented with such advanced-stage cancer that the diagnosis was ascertained by clinical examination and radiologic imaging alone.

Statistical Analysis—Baseline characteristics were compared by BRAF V600E expression using Wilcoxon rank sum and χ² tests. The rate of developing a second primary malignancy at 5, 10, 15, and 20 years after the incident malignant melanoma was estimated with the Kaplan-Meier method. The duration of follow-up was calculated from the incident melanoma date to the second primary malignancy date or the last follow-up date. Patients with a history of the malignancy of interest, except skin cancers, before the incident melanoma date were excluded because it was not possible to distinguish between recurrence of a prior malignancy and a second primary malignancy. Associations of BRAF V600E expression with the development of a second primary malignancy were evaluated with Cox proportional hazards regression models and summarized with hazard ratios (HRs) and 95% CIs; all associations were adjusted for potential confounders such as age at the incident melanoma, year of the incident melanoma, and sex.

Results

Demographics—Table 1 shows the demographic and melanoma-specific characteristics of the 380 patients evaluated for mutant BRAF V600E expression. At last follow-up, 48 patients had died at a median (interquartile range [IQR]) of 6.7 (1.7–14.0) years after the incident melanoma. The median (IQR) duration of follow-up for the 332 living patients was 11.8 (9.1–18.3) years. Three hundred seventy-eight (99%) patients were White. One hundred thirty-three (35%) and 247 (65%) patients were confirmed to have BRAF V600E–positive and BRAF V600E–negative melanomas, respectively.

Cumulative Incidence of Second Primary Melanoma—Of 133 patients with positive BRAF V600E expression, we identified 14 (10.5%), 1 (0.8%), and 1 (0.8%) who had 1, 2, and 4 subsequent melanomas, respectively. Of the 247 patients with negative BRAF V600E expression, we identified 15 (6%), 4 (1.6%), 2 (0.8%), and 1 (0.4%) patients who had 1, 2, 3, and 4 subsequent melanomas, respectively; BRAF V600E expression was not associated with the number of subsequent melanomas (P=.37; Wilcoxon rank sum test). The cumulative incidences of developing a second primary melanoma (n=38 among the 380 patients studied) at 5, 10, 15, and 20 years after the incident melanoma were 5.3%, 7.6%, 8.1%, and 14.6%, respectively.

Cumulative Incidence of All Second Primary Malignancies—Of the 380 patients studied, 60 (16%) had at least 1 malignancy diagnosed before the incident melanoma. Of the remaining 320 patients, 104 later had at least 1 malignancy develop, including a second primary melanoma, at a median (IQR) of 8.0 (2.7–16.2) years after the incident melanoma; the 104 patients with at least 1 subsequent malignancy included 40 with BRAF-positive and 64 with BRAF-negative melanomas. The cumulative incidences of developing at least 1 malignancy of any kind at 5, 10, 15, and 20 years after the incident melanoma were 15.0%, 20.5%, 31.2%, and 47.0%, respectively. Table 2 shows the number of patients with at least 1 second primary malignancy after the incident melanoma stratified by BRAF status.

BRAF V600E Expression and Association With Second Primary Malignancy—The eTable shows the associations of mutant BRAF V600E expression status with the development of a new primary malignancy. Malignancies affecting fewer than 10 patients were excluded from the analysis because there were too few events to support the Cox model. Positive BRAF V600E expression was associated with subsequent development of BCCs (HR, 2.32; 95% CI, 1.35-3.99; P=.002) and the development of all combined second primary malignancies excluding melanoma (HR, 1.65; 95% CI, 1.06-2.56; P=.03). However, BRAF V600E status was no longer a significant factor when all second primary malignancies, including second melanomas, were considered (P=.06). Table 3 shows the 5-, 10-, 15-, and 20-year cumulative incidences of all second primary malignancies according to mutant BRAF status.

Comment

Association of BRAF V600E Expression With Second Primary Malignancies—BRAF V600E expression of an incident melanoma was associated with the development of all combined second primary malignancies excluding melanoma; however, this association was not statistically significant when second primary melanomas were included. A possible explanation is that individuals with more than 1 primary melanoma possess additional genetic risk—CDKN2A or CDKN4 gene mutations or MC1R variation—that outweighed the effect of BRAF expression in the statistical analysis.

The 5- and 10-year cumulative incidences of all second primary malignancies excluding second primary melanoma were similar between BRAF-positive and BRAF-negative melanoma, but the 15- and 20-year cumulative incidences were greater for the BRAF-positive cohort. This could reflect the association of BRAF expression with BCCs and the increased likelihood of their occurrence with cumulative sun exposure and advancing age. BRAF expression was associated with the development of BCCs, but the reason for this association was unclear. BRAF-mutated melanoma occurs more frequently on sun-protected sites,²⁰ whereas sporadic BCC generally occurs on sun-exposed sites. However, BRAF-mutated melanoma is associated with high levels of ambient UV exposure early in life, particularly birth through 20 years of age,²¹ and we speculate that such early UV exposure influences the later development of BCCs. The lack of an association between BRAF positivity and the development of other specific cancers is possibly because the mutation is somatic and not inherited or germline, as with the CDKN2A mutation, and/or because of the small size of our cohorts.

Development of BRAF-Mutated Cancers—It currently is not understood why the same somatic mutation can cause different types of cancer. A recent translational research study showed that in mice models, precursor cells of the pancreas and bile duct responded differently when exposed to PIK3CA and KRAS oncogenes, and tumorigenesis is influenced by specific cooperating genetic events in the tissue microenvironment. Future research investigating these molecular interactions may lead to better understanding of cancer pathogenesis and direct the design of new targeted therapies.^22,23

Regarding environmental influences on the development of BRAF-mutated cancers, we found 1 population-based study that identified an association between high iodine content of drinking water and the prevalence of T1799A BRAF papillary thyroid carcinoma in 5 regions in China.²⁴ Another study identified an increased risk for colorectal cancer and nonmelanoma skin cancer in the first-degree relatives of index patients with BRAF V600E colorectal cancer.²⁵ Two studies by institutions in China and Sweden reported the frequency of BRAF mutations in cohorts of patients with melanoma.^26,27

Additional studies investigating a possible association between BRAF-mutated melanoma and other cancers with larger numbers of participants than in our study may become more feasible in the future with increased routine genetic testing of biopsied cancers.

Study Limitations—Limitations of this retrospective epidemiologic study include the possibility of ascertainment bias during data collection. We did not account for known risk factors for cancer (eg, excessive sun exposure, smoking). The Olmsted County population is mostly White, and residents have relatively easy access to health care; these factors should be considered when generalizing the results to other populations. Basal cell carcinomas are common skin cancers, and there may be other risk factors influencing the development of BCCs in our cohort. BRAF mutation analysis was available in only a small number of patients (n=380; aged 18–60 years), which would have reduced our capacity to identify statistically significant associations. A positive BRAF result did not differentiate between high and low expression levels, but expression levels may affect patient outcomes. One study showed that high BRAF expression correlated with significantly poorer overall (P=.009) and disease-specific 5-year survival (P=.007) for 232 patients with primary melanoma.²⁸

The main clinical implications from this study are that we do not have enough evidence to recommend BRAF testing for all incident melanomas, and BRAF-mutated melanomas cannot be associated with increased risk for developing other forms of cancer, with the possible exception of BCCs. Future research should assess BRAF mutation status of any second primary malignancies that arise after an incident BRAF-positive melanoma.

Conclusion

Physicians should be aware of the risk for a second primary malignancy after an incident melanoma, and we emphasize the importance of long-term cancer surveillance. The association between BRAF expression in incident melanomas and a higher rate of BCC development may provide indirect evidence that high levels of UV light exposure in early life can increase the risk for BCCs later. Although BRAF mutations occur in several nonmelanoma cancers, further studies are needed to determine whether BRAF tissue expression in melanoma affects the development of other cancers.

Acknowledgment—We thank Ms. Jayne H. Feind (Rochester, Minnesota) for assistance with study coordination.

Approximately 50% of melanomas contain BRAF mutations, which occur in a greater proportion of melanomas found on sites of intermittent sun exposure.¹BRAF-mutated melanomas have been associated with high levels of early-life ambient UV exposure, especially between ages 0 and 20 years.² In addition, studies have shown that BRAF-mutated melanomas commonly are found on the trunk and extremities.^1-3BRAF mutations also have been associated with younger age, superficial spreading subtype and low tumor thickness, absence of dermal melanocyte mitosis, low Ki-67 score, low phospho-histone H3 score, pigmented melanoma, advanced melanoma stage, and conjunctival melanoma.^4-7BRAF mutations are found more frequently in metastatic melanoma lesions than primary melanomas, suggesting that BRAF mutations may be acquired during metastasis.⁸ Studies have shown different conclusions on the effect of BRAF mutation on melanoma-related death.^5,9,10

The aim of this study was to identify trends in BRAF V600E–mutated melanoma according to age, sex, and melanoma-specific survival among Olmsted County, Minnesota, residents with a first diagnosis of melanoma at 18 to 60 years of age.

Methods

In total, 638 patients aged 18 to 60 years who resided in Olmsted County and had a first lifetime diagnosis of cutaneous melanoma between 1970 and 2009 were retrospectively identified as a part of the Rochester Epidemiology Project (REP). The REP is a health records linkage system that encompasses almost all sources of medical care available to the local population of Olmsted County.¹¹ This study was approved by the Mayo Clinic Institutional Review Board (Rochester, Minnesota).

Of the 638 individuals identified in the REP, 536 had been seen at Mayo Clinic and thus potentially had tissue blocks available for the study of BRAF mutation expression. Of these 536 patients, 156 did not have sufficient residual tissue available. As a result, 380 (60%) of the original 638 patients had available blocks with sufficient tissue for immunohistochemical analysis of BRAF expression. Only primary cutaneous melanomas were included in the present study.

All specimens were reviewed by a board-certified dermatopathologist (J.S.L.) for appropriateness of inclusion, which involved confirmation of the diagnosis of melanoma, histologic type of melanoma, and presence of sufficient residual tissue for immunohistochemical stains.

All specimens were originally diagnosed as malignant melanoma at the time of clinical care by at least 2 board-certified dermatopathologists. For the purposes of this study, all specimens were rereviewed for diagnostic accuracy. We required that specimens exhibit severe cytologic and architectural atypia as well as other features favoring melanoma, such as consumption of rete pegs, pagetosis, confluence of junctional melanocytes, evidence of regression, lack of maturation of melanocytes with descent into the dermis, or mitotic figures among the dermal melanocyte population.

The available tissue blocks were retrieved, sectioned, confirmed as melanoma, and stained with a mouse antihuman BRAF V600E monoclonal antibody (clone VE1; Spring Bioscience) to determine the presence of a BRAF V600E mutation. BRAF staining was evaluated in conjunction with a review of the associated slides stained with hematoxylin and eosin. Cytoplasmic staining of melanocytes for BRAF was graded as negative, focal or partial positive (<50% of tumor), or diffuse positive (>50% of tumor)(Figure 1). When a melanoma arose in association with a nevus, we considered only the melanoma component for BRAF staining. We categorized the histologic type as superficial spreading, nodular, or lentigo maligna, and the location as head and neck, trunk, or extremities.

Results

Clinical and Tumor Characteristics—Of the 380 tissue specimens that underwent BRAF V600E analysis, 247 had negative staining; 106 had diffuse strong staining; and 27 had focal or partial staining. In total, 133 (35%) were positive, either partially or diffusely. The median age for patients who had negative staining was 45 years; for those with positive staining, it was 41 years (P=.07).

The patients who met inclusion criteria (n=380) were compared with those who were excluded (n=258)(eTable 1). The groups were similar on the basis of sex; age; and melanoma location, stage, and histologic subtype. However, some evidence showed that patients included in the study received the diagnosis of melanoma more recently (1970-1989, 13.2%; 1990-1999, 28.7%; 2000-2009, 58.2%) than those who were excluded (1970-1989, 24.7%; 1990-1999, 23.5%; 2000-2009, 51.8%)(P=.02).

BRAF V600E expression was more commonly found in superficial spreading (37.7%) and nodular melanomas (35.0%) than in situ melanomas (17.1%)(P=.01). Other characteristics of BRAF V600E expression are described in eTable 2. Overall, invasive and advanced melanomas were significantly more likely to harbor BRAF V600E expression than noninvasive melanomas (39.6% and 37.9%, respectively, vs 17.9%; P=.003). However, advanced melanomas more commonly expressed BRAF positivity among women, and invasive melanomas more commonly expressed BRAF positivity among men (eTable 2).

Survival—Survival analyses were limited to 297 patients with confirmed invasive or advanced disease. Of these, 180 (61%) had no BRAF V600E staining; 25 (8%) had partial staining; and 92 (31%) had diffuse positive staining. In total, 117 patients (39%) had a BRAF-mutated melanoma.

Among the patients still alive, the median (interquartile range [IQR]) duration of follow-up was 10.2 (7.0-16.8) years. Thirty-nine patients with invasive or advanced disease had died of any cause at a median (IQR) of 3.0 (1.3-10.2) years after diagnosis. In total, 26 patients died of melanoma at a median (IQR) follow-up of 2.5 (1.3-7.4) years after diagnosis. Eight women and 18 men died of malignant melanoma. Five deaths occurred because of malignant melanoma among patients aged 18 to 39 years, and 21 occurred among patients aged 40 to 60 years. In the 18- to 39-year-old group, all 5 deaths were among patients with a BRAF-positive melanoma. Estimated disease-specific survival rate (95% CI; number still at risk) at 5, 10, 15, and 20 years after diagnosis was 94% (91%-97%; 243), 91% (87%-95%; 142), 89% (85%-94%; 87), and 88% (83%-93%; 45), respectively.

Comment

We found that melanomas with BRAF mutations were more likely in advanced and invasive melanoma. The frequency of BRAF mutations among melanomas that were considered advanced was higher in women than men. Although the number of deaths was limited, women with a melanoma with BRAF expression were more likely to die of melanoma, young adults with a BRAF-mutated melanoma had an almost 10-fold increased risk of dying from any cause, and middle-aged adults showed no increased risk of death. These findings suggest that young adults who are genetically prone to a BRAF-mutated melanoma could be at a disadvantage for all-cause mortality. Although this finding was significant, the 95% CI was large, and further studies would be warranted before sound conclusions could be made.

Melanoma has been increasing in incidence across all age groups in Olmsted County over the last 4 decades.^12-14 However, our results show that the percentage of BRAF-mutated melanomas in this population has been stable over time, with no statistically significant difference by age or sex. Other confounding factors may have an influence, such as increased rates of early detection and diagnosis of melanoma in contemporary times. Our data suggest that patients included in the BRAF-mutation analysis study had received the diagnosis of melanoma more recently than those who were excluded from the study, which could be due to older melanomas being less likely to have adequate tissue specimens available for immunohistochemical staining/evaluation.

Prior research has shown that BRAF-mutated melanomas typically occur on the trunk and are more likely in individuals with more than 14 nevi on the back.² In the present cohort, BRAF-positive melanomas had a predisposition toward the trunk but also were found on the head, neck, and extremities—areas that are more likely to have long-term sun damage. One suggestion is that 2 distinct pathways for melanoma development exist: one associated with a large number of melanocytic nevi (that is more prone to genetic mutations in melanocytes) and the other associated with long-term sun exposure.^15,16 The combination of these hypotheses suggests that individuals who are prone to the development of large numbers of nevi may require sun exposure for the initial insult, but the development of melanoma may be carried out by other factors after this initial sun exposure insult, whereas individuals without large numbers of nevi who may have less genetic risk may require continued long-term sun exposure for melanoma to develop.¹⁷

Our study had limitations, including the small numbers of deaths overall and cause-specific deaths of metastatic melanoma, which limited our ability to conduct more extensive multivariable modeling. Also, the retrospective nature and time frame of looking back 4 decades did not allow us to have information sufficient to categorize some patients as having dysplastic nevus syndrome or not, which would be a potentially interesting variable to include in the analysis. Because the number of deaths in the 18- to 39-year-old cohort was only 5, further statistical comparison regarding tumor type and other variables pertaining to BRAF positivity were not possible. In addition, our data were collected from patients residing in a single geographic county (Olmsted County, Minnesota), which may limit generalizability. Lastly, BRAF V600E mutations were identified through immunostaining only, not molecular data, so it is possible some patients had false-negative immunohistochemistry findings and thus were not identified.

Conclusion

BRAF-mutated melanomas were found in 35% of our cohort, with no significant change in the percentage of melanomas with BRAF V600E mutations over the last 4 decades in this population. In addition, no differences or significant trends existed according to sex and BRAF-mutated melanoma development. Women with BRAF-mutated melanomas were more likely to die of metastatic melanoma than men, and young adults with BRAF-mutated melanomas had a higher all-cause mortality risk. Further research is needed to decipher what effect BRAF-mutated melanomas have on metastasis and cause-specific death in women as well as all-cause mortality in young adults.

Acknowledgment—The authors are indebted to Scientific Publications, Mayo Clinic (Rochester, Minnesota).

Approximately 50% of melanomas contain BRAF mutations, which occur in a greater proportion of melanomas found on sites of intermittent sun exposure.¹BRAF-mutated melanomas have been associated with high levels of early-life ambient UV exposure, especially between ages 0 and 20 years.² In addition, studies have shown that BRAF-mutated melanomas commonly are found on the trunk and extremities.^1-3BRAF mutations also have been associated with younger age, superficial spreading subtype and low tumor thickness, absence of dermal melanocyte mitosis, low Ki-67 score, low phospho-histone H3 score, pigmented melanoma, advanced melanoma stage, and conjunctival melanoma.^4-7BRAF mutations are found more frequently in metastatic melanoma lesions than primary melanomas, suggesting that BRAF mutations may be acquired during metastasis.⁸ Studies have shown different conclusions on the effect of BRAF mutation on melanoma-related death.^5,9,10

The aim of this study was to identify trends in BRAF V600E–mutated melanoma according to age, sex, and melanoma-specific survival among Olmsted County, Minnesota, residents with a first diagnosis of melanoma at 18 to 60 years of age.

Methods

In total, 638 patients aged 18 to 60 years who resided in Olmsted County and had a first lifetime diagnosis of cutaneous melanoma between 1970 and 2009 were retrospectively identified as a part of the Rochester Epidemiology Project (REP). The REP is a health records linkage system that encompasses almost all sources of medical care available to the local population of Olmsted County.¹¹ This study was approved by the Mayo Clinic Institutional Review Board (Rochester, Minnesota).

Of the 638 individuals identified in the REP, 536 had been seen at Mayo Clinic and thus potentially had tissue blocks available for the study of BRAF mutation expression. Of these 536 patients, 156 did not have sufficient residual tissue available. As a result, 380 (60%) of the original 638 patients had available blocks with sufficient tissue for immunohistochemical analysis of BRAF expression. Only primary cutaneous melanomas were included in the present study.

All specimens were reviewed by a board-certified dermatopathologist (J.S.L.) for appropriateness of inclusion, which involved confirmation of the diagnosis of melanoma, histologic type of melanoma, and presence of sufficient residual tissue for immunohistochemical stains.

All specimens were originally diagnosed as malignant melanoma at the time of clinical care by at least 2 board-certified dermatopathologists. For the purposes of this study, all specimens were rereviewed for diagnostic accuracy. We required that specimens exhibit severe cytologic and architectural atypia as well as other features favoring melanoma, such as consumption of rete pegs, pagetosis, confluence of junctional melanocytes, evidence of regression, lack of maturation of melanocytes with descent into the dermis, or mitotic figures among the dermal melanocyte population.

The available tissue blocks were retrieved, sectioned, confirmed as melanoma, and stained with a mouse antihuman BRAF V600E monoclonal antibody (clone VE1; Spring Bioscience) to determine the presence of a BRAF V600E mutation. BRAF staining was evaluated in conjunction with a review of the associated slides stained with hematoxylin and eosin. Cytoplasmic staining of melanocytes for BRAF was graded as negative, focal or partial positive (<50% of tumor), or diffuse positive (>50% of tumor)(Figure 1). When a melanoma arose in association with a nevus, we considered only the melanoma component for BRAF staining. We categorized the histologic type as superficial spreading, nodular, or lentigo maligna, and the location as head and neck, trunk, or extremities.

Results

Clinical and Tumor Characteristics—Of the 380 tissue specimens that underwent BRAF V600E analysis, 247 had negative staining; 106 had diffuse strong staining; and 27 had focal or partial staining. In total, 133 (35%) were positive, either partially or diffusely. The median age for patients who had negative staining was 45 years; for those with positive staining, it was 41 years (P=.07).

The patients who met inclusion criteria (n=380) were compared with those who were excluded (n=258)(eTable 1). The groups were similar on the basis of sex; age; and melanoma location, stage, and histologic subtype. However, some evidence showed that patients included in the study received the diagnosis of melanoma more recently (1970-1989, 13.2%; 1990-1999, 28.7%; 2000-2009, 58.2%) than those who were excluded (1970-1989, 24.7%; 1990-1999, 23.5%; 2000-2009, 51.8%)(P=.02).

BRAF V600E expression was more commonly found in superficial spreading (37.7%) and nodular melanomas (35.0%) than in situ melanomas (17.1%)(P=.01). Other characteristics of BRAF V600E expression are described in eTable 2. Overall, invasive and advanced melanomas were significantly more likely to harbor BRAF V600E expression than noninvasive melanomas (39.6% and 37.9%, respectively, vs 17.9%; P=.003). However, advanced melanomas more commonly expressed BRAF positivity among women, and invasive melanomas more commonly expressed BRAF positivity among men (eTable 2).

Survival—Survival analyses were limited to 297 patients with confirmed invasive or advanced disease. Of these, 180 (61%) had no BRAF V600E staining; 25 (8%) had partial staining; and 92 (31%) had diffuse positive staining. In total, 117 patients (39%) had a BRAF-mutated melanoma.

Among the patients still alive, the median (interquartile range [IQR]) duration of follow-up was 10.2 (7.0-16.8) years. Thirty-nine patients with invasive or advanced disease had died of any cause at a median (IQR) of 3.0 (1.3-10.2) years after diagnosis. In total, 26 patients died of melanoma at a median (IQR) follow-up of 2.5 (1.3-7.4) years after diagnosis. Eight women and 18 men died of malignant melanoma. Five deaths occurred because of malignant melanoma among patients aged 18 to 39 years, and 21 occurred among patients aged 40 to 60 years. In the 18- to 39-year-old group, all 5 deaths were among patients with a BRAF-positive melanoma. Estimated disease-specific survival rate (95% CI; number still at risk) at 5, 10, 15, and 20 years after diagnosis was 94% (91%-97%; 243), 91% (87%-95%; 142), 89% (85%-94%; 87), and 88% (83%-93%; 45), respectively.

Comment

We found that melanomas with BRAF mutations were more likely in advanced and invasive melanoma. The frequency of BRAF mutations among melanomas that were considered advanced was higher in women than men. Although the number of deaths was limited, women with a melanoma with BRAF expression were more likely to die of melanoma, young adults with a BRAF-mutated melanoma had an almost 10-fold increased risk of dying from any cause, and middle-aged adults showed no increased risk of death. These findings suggest that young adults who are genetically prone to a BRAF-mutated melanoma could be at a disadvantage for all-cause mortality. Although this finding was significant, the 95% CI was large, and further studies would be warranted before sound conclusions could be made.

Melanoma has been increasing in incidence across all age groups in Olmsted County over the last 4 decades.^12-14 However, our results show that the percentage of BRAF-mutated melanomas in this population has been stable over time, with no statistically significant difference by age or sex. Other confounding factors may have an influence, such as increased rates of early detection and diagnosis of melanoma in contemporary times. Our data suggest that patients included in the BRAF-mutation analysis study had received the diagnosis of melanoma more recently than those who were excluded from the study, which could be due to older melanomas being less likely to have adequate tissue specimens available for immunohistochemical staining/evaluation.

Prior research has shown that BRAF-mutated melanomas typically occur on the trunk and are more likely in individuals with more than 14 nevi on the back.² In the present cohort, BRAF-positive melanomas had a predisposition toward the trunk but also were found on the head, neck, and extremities—areas that are more likely to have long-term sun damage. One suggestion is that 2 distinct pathways for melanoma development exist: one associated with a large number of melanocytic nevi (that is more prone to genetic mutations in melanocytes) and the other associated with long-term sun exposure.^15,16 The combination of these hypotheses suggests that individuals who are prone to the development of large numbers of nevi may require sun exposure for the initial insult, but the development of melanoma may be carried out by other factors after this initial sun exposure insult, whereas individuals without large numbers of nevi who may have less genetic risk may require continued long-term sun exposure for melanoma to develop.¹⁷

Our study had limitations, including the small numbers of deaths overall and cause-specific deaths of metastatic melanoma, which limited our ability to conduct more extensive multivariable modeling. Also, the retrospective nature and time frame of looking back 4 decades did not allow us to have information sufficient to categorize some patients as having dysplastic nevus syndrome or not, which would be a potentially interesting variable to include in the analysis. Because the number of deaths in the 18- to 39-year-old cohort was only 5, further statistical comparison regarding tumor type and other variables pertaining to BRAF positivity were not possible. In addition, our data were collected from patients residing in a single geographic county (Olmsted County, Minnesota), which may limit generalizability. Lastly, BRAF V600E mutations were identified through immunostaining only, not molecular data, so it is possible some patients had false-negative immunohistochemistry findings and thus were not identified.

Conclusion

BRAF-mutated melanomas were found in 35% of our cohort, with no significant change in the percentage of melanomas with BRAF V600E mutations over the last 4 decades in this population. In addition, no differences or significant trends existed according to sex and BRAF-mutated melanoma development. Women with BRAF-mutated melanomas were more likely to die of metastatic melanoma than men, and young adults with BRAF-mutated melanomas had a higher all-cause mortality risk. Further research is needed to decipher what effect BRAF-mutated melanomas have on metastasis and cause-specific death in women as well as all-cause mortality in young adults.

Acknowledgment—The authors are indebted to Scientific Publications, Mayo Clinic (Rochester, Minnesota).

Approximately 50% of melanomas contain BRAF mutations, which occur in a greater proportion of melanomas found on sites of intermittent sun exposure.¹BRAF-mutated melanomas have been associated with high levels of early-life ambient UV exposure, especially between ages 0 and 20 years.² In addition, studies have shown that BRAF-mutated melanomas commonly are found on the trunk and extremities.^1-3BRAF mutations also have been associated with younger age, superficial spreading subtype and low tumor thickness, absence of dermal melanocyte mitosis, low Ki-67 score, low phospho-histone H3 score, pigmented melanoma, advanced melanoma stage, and conjunctival melanoma.^4-7BRAF mutations are found more frequently in metastatic melanoma lesions than primary melanomas, suggesting that BRAF mutations may be acquired during metastasis.⁸ Studies have shown different conclusions on the effect of BRAF mutation on melanoma-related death.^5,9,10

The aim of this study was to identify trends in BRAF V600E–mutated melanoma according to age, sex, and melanoma-specific survival among Olmsted County, Minnesota, residents with a first diagnosis of melanoma at 18 to 60 years of age.

Methods

In total, 638 patients aged 18 to 60 years who resided in Olmsted County and had a first lifetime diagnosis of cutaneous melanoma between 1970 and 2009 were retrospectively identified as a part of the Rochester Epidemiology Project (REP). The REP is a health records linkage system that encompasses almost all sources of medical care available to the local population of Olmsted County.¹¹ This study was approved by the Mayo Clinic Institutional Review Board (Rochester, Minnesota).

Of the 638 individuals identified in the REP, 536 had been seen at Mayo Clinic and thus potentially had tissue blocks available for the study of BRAF mutation expression. Of these 536 patients, 156 did not have sufficient residual tissue available. As a result, 380 (60%) of the original 638 patients had available blocks with sufficient tissue for immunohistochemical analysis of BRAF expression. Only primary cutaneous melanomas were included in the present study.

All specimens were reviewed by a board-certified dermatopathologist (J.S.L.) for appropriateness of inclusion, which involved confirmation of the diagnosis of melanoma, histologic type of melanoma, and presence of sufficient residual tissue for immunohistochemical stains.

All specimens were originally diagnosed as malignant melanoma at the time of clinical care by at least 2 board-certified dermatopathologists. For the purposes of this study, all specimens were rereviewed for diagnostic accuracy. We required that specimens exhibit severe cytologic and architectural atypia as well as other features favoring melanoma, such as consumption of rete pegs, pagetosis, confluence of junctional melanocytes, evidence of regression, lack of maturation of melanocytes with descent into the dermis, or mitotic figures among the dermal melanocyte population.

The available tissue blocks were retrieved, sectioned, confirmed as melanoma, and stained with a mouse antihuman BRAF V600E monoclonal antibody (clone VE1; Spring Bioscience) to determine the presence of a BRAF V600E mutation. BRAF staining was evaluated in conjunction with a review of the associated slides stained with hematoxylin and eosin. Cytoplasmic staining of melanocytes for BRAF was graded as negative, focal or partial positive (<50% of tumor), or diffuse positive (>50% of tumor)(Figure 1). When a melanoma arose in association with a nevus, we considered only the melanoma component for BRAF staining. We categorized the histologic type as superficial spreading, nodular, or lentigo maligna, and the location as head and neck, trunk, or extremities.

Results

Clinical and Tumor Characteristics—Of the 380 tissue specimens that underwent BRAF V600E analysis, 247 had negative staining; 106 had diffuse strong staining; and 27 had focal or partial staining. In total, 133 (35%) were positive, either partially or diffusely. The median age for patients who had negative staining was 45 years; for those with positive staining, it was 41 years (P=.07).

The patients who met inclusion criteria (n=380) were compared with those who were excluded (n=258)(eTable 1). The groups were similar on the basis of sex; age; and melanoma location, stage, and histologic subtype. However, some evidence showed that patients included in the study received the diagnosis of melanoma more recently (1970-1989, 13.2%; 1990-1999, 28.7%; 2000-2009, 58.2%) than those who were excluded (1970-1989, 24.7%; 1990-1999, 23.5%; 2000-2009, 51.8%)(P=.02).

BRAF V600E expression was more commonly found in superficial spreading (37.7%) and nodular melanomas (35.0%) than in situ melanomas (17.1%)(P=.01). Other characteristics of BRAF V600E expression are described in eTable 2. Overall, invasive and advanced melanomas were significantly more likely to harbor BRAF V600E expression than noninvasive melanomas (39.6% and 37.9%, respectively, vs 17.9%; P=.003). However, advanced melanomas more commonly expressed BRAF positivity among women, and invasive melanomas more commonly expressed BRAF positivity among men (eTable 2).

Survival—Survival analyses were limited to 297 patients with confirmed invasive or advanced disease. Of these, 180 (61%) had no BRAF V600E staining; 25 (8%) had partial staining; and 92 (31%) had diffuse positive staining. In total, 117 patients (39%) had a BRAF-mutated melanoma.

Among the patients still alive, the median (interquartile range [IQR]) duration of follow-up was 10.2 (7.0-16.8) years. Thirty-nine patients with invasive or advanced disease had died of any cause at a median (IQR) of 3.0 (1.3-10.2) years after diagnosis. In total, 26 patients died of melanoma at a median (IQR) follow-up of 2.5 (1.3-7.4) years after diagnosis. Eight women and 18 men died of malignant melanoma. Five deaths occurred because of malignant melanoma among patients aged 18 to 39 years, and 21 occurred among patients aged 40 to 60 years. In the 18- to 39-year-old group, all 5 deaths were among patients with a BRAF-positive melanoma. Estimated disease-specific survival rate (95% CI; number still at risk) at 5, 10, 15, and 20 years after diagnosis was 94% (91%-97%; 243), 91% (87%-95%; 142), 89% (85%-94%; 87), and 88% (83%-93%; 45), respectively.

Comment

We found that melanomas with BRAF mutations were more likely in advanced and invasive melanoma. The frequency of BRAF mutations among melanomas that were considered advanced was higher in women than men. Although the number of deaths was limited, women with a melanoma with BRAF expression were more likely to die of melanoma, young adults with a BRAF-mutated melanoma had an almost 10-fold increased risk of dying from any cause, and middle-aged adults showed no increased risk of death. These findings suggest that young adults who are genetically prone to a BRAF-mutated melanoma could be at a disadvantage for all-cause mortality. Although this finding was significant, the 95% CI was large, and further studies would be warranted before sound conclusions could be made.

Melanoma has been increasing in incidence across all age groups in Olmsted County over the last 4 decades.^12-14 However, our results show that the percentage of BRAF-mutated melanomas in this population has been stable over time, with no statistically significant difference by age or sex. Other confounding factors may have an influence, such as increased rates of early detection and diagnosis of melanoma in contemporary times. Our data suggest that patients included in the BRAF-mutation analysis study had received the diagnosis of melanoma more recently than those who were excluded from the study, which could be due to older melanomas being less likely to have adequate tissue specimens available for immunohistochemical staining/evaluation.

Prior research has shown that BRAF-mutated melanomas typically occur on the trunk and are more likely in individuals with more than 14 nevi on the back.² In the present cohort, BRAF-positive melanomas had a predisposition toward the trunk but also were found on the head, neck, and extremities—areas that are more likely to have long-term sun damage. One suggestion is that 2 distinct pathways for melanoma development exist: one associated with a large number of melanocytic nevi (that is more prone to genetic mutations in melanocytes) and the other associated with long-term sun exposure.^15,16 The combination of these hypotheses suggests that individuals who are prone to the development of large numbers of nevi may require sun exposure for the initial insult, but the development of melanoma may be carried out by other factors after this initial sun exposure insult, whereas individuals without large numbers of nevi who may have less genetic risk may require continued long-term sun exposure for melanoma to develop.¹⁷

Our study had limitations, including the small numbers of deaths overall and cause-specific deaths of metastatic melanoma, which limited our ability to conduct more extensive multivariable modeling. Also, the retrospective nature and time frame of looking back 4 decades did not allow us to have information sufficient to categorize some patients as having dysplastic nevus syndrome or not, which would be a potentially interesting variable to include in the analysis. Because the number of deaths in the 18- to 39-year-old cohort was only 5, further statistical comparison regarding tumor type and other variables pertaining to BRAF positivity were not possible. In addition, our data were collected from patients residing in a single geographic county (Olmsted County, Minnesota), which may limit generalizability. Lastly, BRAF V600E mutations were identified through immunostaining only, not molecular data, so it is possible some patients had false-negative immunohistochemistry findings and thus were not identified.

Conclusion

BRAF-mutated melanomas were found in 35% of our cohort, with no significant change in the percentage of melanomas with BRAF V600E mutations over the last 4 decades in this population. In addition, no differences or significant trends existed according to sex and BRAF-mutated melanoma development. Women with BRAF-mutated melanomas were more likely to die of metastatic melanoma than men, and young adults with BRAF-mutated melanomas had a higher all-cause mortality risk. Further research is needed to decipher what effect BRAF-mutated melanomas have on metastasis and cause-specific death in women as well as all-cause mortality in young adults.

Acknowledgment—The authors are indebted to Scientific Publications, Mayo Clinic (Rochester, Minnesota).