Commentary: Axillary Surgery, PM2.5, and Treatment With Tucatinib in Breast Cancer, November 2023

Support for axillary surgery de-escalation for select patients with early-stage breast cancer has been demonstrated in prior studies,^1,2 leading to widespread use of sentinel lymph node biopsy (SLNB) for axillary staging for many patients. For example, the phase 3 randomized ACOSOG Z0011 trial showed that among women with T1/2 breast cancer, without palpable lymph nodes and one to two sentinel lymph nodes positive, survival outcomes were noninferior for sentinel lymph node dissection vs axillary lymph node dissection.¹ The SOUND (Sentinel Node vs Observation After Axillary Ultra-Sound) trial was a phase 3 prospective randomized study that included 1405 women with early breast cancer, tumor size ≤ 2 cm, and negative preoperative axillary ultrasound, and was designed to investigate the effect of axillary surgery omission in these patients (Gentilini et al). Five-year distant disease-free survival, the primary endpoint, was 97.7% in the SLNB group and 98.0% in the no-axillary-surgery group (log-rank P = .67; hazard ratio [HR] 0.84, noninferiority P = .02). Rates of locoregional relapse (1.7% vs 1.6%), distant metastases (1.8% vs 2.0%), and deaths (3.0% vs 2.6%) were similar in the SLNB group compared with the no-axillary-surgery group, respectively. Furthermore, adjuvant treatments were not significantly different between the two groups, indicating that tumor biology/genomics may have an expanding role in tailoring adjuvant therapy compared with clinicopathologic features. The results of this study suggest that axillary surgery omission can be considered in patients with ≤ T2 early breast cancer and negative axillary ultrasound when absence of this pathologic information does not affect the adjuvant treatment plan.

Hormone receptor–positive breast cancer is the most common subtype, with established risk factors including exposure to exogenous hormones, reproductive history, and lifestyle components (alcohol intake, obesity). There are also less-recognized environmental influences that may disrupt endocrine pathways and, as a result, affect tumor development. Fine particulate matter (PM_2.5), produced by combustion processes (vehicles, industrial facilities), burning wood, and fires, among other sources, is composed of various airborne pollutants (metals, organic compounds, ammonium, nitrate, ozone, sulfate, etc.). Prior studies evaluating the association of PM_2.5 and breast cancer development have shown mixed results.^3,4 A prospective US cohort study including 196,905 women without a prior history of breast cancer estimated historical annual average PM_2.5 concentrations between 1980 and 1984 (10 years prior to enrollment) (White et al). A total of 15,870 breast cancer cases were identified, and a 10 μg/m³ increase in PM_2.5 was associated with an 8% increase in overall breast cancer incidence (HR 1.08; 95% CI 1.02-1.13). The association was observed for estrogen-receptor (ER)-positive (HR 1.10; 95% CI 1.04-1.17) but not ER-negative tumors. Future studies focusing on historic exposures, investigating geographic differences and the resultant effect on cancer development, are of interest.

HER2CLIMB was a pivotal phase 3 randomized, double-blinded trial that demonstrated significant improvement in survival outcomes with the combination of tucatinib/trastuzumab/capecitabine vs tucatinib/trastuzumab/placebo among patients with previously treated human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer.⁵ Real-world data help inform our daily practice because patients enrolled in clinical trials do not always accurately represent the general population. A retrospective cohort study including 3449 patients with HER2-positive metastatic breast cancer evaluated outcomes with tucatinib in a real-world setting, demonstrating results similar to those seen in HER2CLIMB. Among all patients who received tucatinib (n = 216), median real-world time to treatment discontinuation was 6.5 months (95% CI 5.4-8.8), median real-world time to next treatment (which can serve as a proxy for progression-free survival) was 8.7 months (95% CI 6.8-10.7), and real-world overall survival was 26.6 months (95% CI 20.2–not reached). Median real-world time to treatment discontinuation was 8.1 months (95% CI 5.7-9.5) for patients who received the approved tucatinib triplet combination after one or more HER2-directed regimens in the metastatic setting and 9.4 months (95% CI 6.3-14.1) for those receiving it in the second- or third-line setting (Kaufman et al). These results support the efficacy of tucatinib in a real-world population, suggesting that earlier use (second or third line) may result in better outcomes. Future studies will continue to address the positioning of tucatinib in the treatment algorithm for HER2-positive metastatic breast cancer, including the evaluation of novel combinations.

Additional References

1. Giuliano AE et al. Effect of axillary dissection vs no axillary dissection on 10-year overall survival among women with invasive breast cancer and sentinel node metastasis: The ACOSOG Z0011 (Alliance) randomized clinical trial. JAMA. 2017;318:918-926. doi: 10.1001/jama.2017.11470 
2. Bartels SAL, Donker M, et al. Radiotherapy or surgery of the axilla after a positive sentinel node in breast cancer: 10-year results of the randomized controlled EORTC 10981-22023 AMAROS Trial. J Clin Oncol. 2023;41:2159-2165. doi: 10.1200/JCO.22.01565
3. Gabet S, Lemarchand C, Guénel P, Slama R. Breast cancer risk in association with atmospheric pollution exposure: A meta-analysis of effect estimates followed by a health impact assessment. Environ Health Perspect. 2021;129:57012. doi: 10.1289/EHP8419
4. Hvidtfeldt UA et al. Breast cancer incidence in relation to long-term low-level exposure to air pollution in the ELAPSE pooled cohort. Cancer Epidemiol Biomarkers Prev. 2023;32:105-113. doi: 10.1158/1055-9965.EPI-22-0720  
5. Murthy RK et al. Tucatinib, trastuzumab, and capecitabine for HER2-positive metastatic breast cancer. N Engl J Med. 2020;382:597-609. doi:10.1056/NEJMoa1914609

Support for axillary surgery de-escalation for select patients with early-stage breast cancer has been demonstrated in prior studies,^1,2 leading to widespread use of sentinel lymph node biopsy (SLNB) for axillary staging for many patients. For example, the phase 3 randomized ACOSOG Z0011 trial showed that among women with T1/2 breast cancer, without palpable lymph nodes and one to two sentinel lymph nodes positive, survival outcomes were noninferior for sentinel lymph node dissection vs axillary lymph node dissection.¹ The SOUND (Sentinel Node vs Observation After Axillary Ultra-Sound) trial was a phase 3 prospective randomized study that included 1405 women with early breast cancer, tumor size ≤ 2 cm, and negative preoperative axillary ultrasound, and was designed to investigate the effect of axillary surgery omission in these patients (Gentilini et al). Five-year distant disease-free survival, the primary endpoint, was 97.7% in the SLNB group and 98.0% in the no-axillary-surgery group (log-rank P = .67; hazard ratio [HR] 0.84, noninferiority P = .02). Rates of locoregional relapse (1.7% vs 1.6%), distant metastases (1.8% vs 2.0%), and deaths (3.0% vs 2.6%) were similar in the SLNB group compared with the no-axillary-surgery group, respectively. Furthermore, adjuvant treatments were not significantly different between the two groups, indicating that tumor biology/genomics may have an expanding role in tailoring adjuvant therapy compared with clinicopathologic features. The results of this study suggest that axillary surgery omission can be considered in patients with ≤ T2 early breast cancer and negative axillary ultrasound when absence of this pathologic information does not affect the adjuvant treatment plan.

Hormone receptor–positive breast cancer is the most common subtype, with established risk factors including exposure to exogenous hormones, reproductive history, and lifestyle components (alcohol intake, obesity). There are also less-recognized environmental influences that may disrupt endocrine pathways and, as a result, affect tumor development. Fine particulate matter (PM_2.5), produced by combustion processes (vehicles, industrial facilities), burning wood, and fires, among other sources, is composed of various airborne pollutants (metals, organic compounds, ammonium, nitrate, ozone, sulfate, etc.). Prior studies evaluating the association of PM_2.5 and breast cancer development have shown mixed results.^3,4 A prospective US cohort study including 196,905 women without a prior history of breast cancer estimated historical annual average PM_2.5 concentrations between 1980 and 1984 (10 years prior to enrollment) (White et al). A total of 15,870 breast cancer cases were identified, and a 10 μg/m³ increase in PM_2.5 was associated with an 8% increase in overall breast cancer incidence (HR 1.08; 95% CI 1.02-1.13). The association was observed for estrogen-receptor (ER)-positive (HR 1.10; 95% CI 1.04-1.17) but not ER-negative tumors. Future studies focusing on historic exposures, investigating geographic differences and the resultant effect on cancer development, are of interest.

HER2CLIMB was a pivotal phase 3 randomized, double-blinded trial that demonstrated significant improvement in survival outcomes with the combination of tucatinib/trastuzumab/capecitabine vs tucatinib/trastuzumab/placebo among patients with previously treated human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer.⁵ Real-world data help inform our daily practice because patients enrolled in clinical trials do not always accurately represent the general population. A retrospective cohort study including 3449 patients with HER2-positive metastatic breast cancer evaluated outcomes with tucatinib in a real-world setting, demonstrating results similar to those seen in HER2CLIMB. Among all patients who received tucatinib (n = 216), median real-world time to treatment discontinuation was 6.5 months (95% CI 5.4-8.8), median real-world time to next treatment (which can serve as a proxy for progression-free survival) was 8.7 months (95% CI 6.8-10.7), and real-world overall survival was 26.6 months (95% CI 20.2–not reached). Median real-world time to treatment discontinuation was 8.1 months (95% CI 5.7-9.5) for patients who received the approved tucatinib triplet combination after one or more HER2-directed regimens in the metastatic setting and 9.4 months (95% CI 6.3-14.1) for those receiving it in the second- or third-line setting (Kaufman et al). These results support the efficacy of tucatinib in a real-world population, suggesting that earlier use (second or third line) may result in better outcomes. Future studies will continue to address the positioning of tucatinib in the treatment algorithm for HER2-positive metastatic breast cancer, including the evaluation of novel combinations.

Additional References

1. Giuliano AE et al. Effect of axillary dissection vs no axillary dissection on 10-year overall survival among women with invasive breast cancer and sentinel node metastasis: The ACOSOG Z0011 (Alliance) randomized clinical trial. JAMA. 2017;318:918-926. doi: 10.1001/jama.2017.11470 
2. Bartels SAL, Donker M, et al. Radiotherapy or surgery of the axilla after a positive sentinel node in breast cancer: 10-year results of the randomized controlled EORTC 10981-22023 AMAROS Trial. J Clin Oncol. 2023;41:2159-2165. doi: 10.1200/JCO.22.01565
3. Gabet S, Lemarchand C, Guénel P, Slama R. Breast cancer risk in association with atmospheric pollution exposure: A meta-analysis of effect estimates followed by a health impact assessment. Environ Health Perspect. 2021;129:57012. doi: 10.1289/EHP8419
4. Hvidtfeldt UA et al. Breast cancer incidence in relation to long-term low-level exposure to air pollution in the ELAPSE pooled cohort. Cancer Epidemiol Biomarkers Prev. 2023;32:105-113. doi: 10.1158/1055-9965.EPI-22-0720  
5. Murthy RK et al. Tucatinib, trastuzumab, and capecitabine for HER2-positive metastatic breast cancer. N Engl J Med. 2020;382:597-609. doi:10.1056/NEJMoa1914609

Support for axillary surgery de-escalation for select patients with early-stage breast cancer has been demonstrated in prior studies,^1,2 leading to widespread use of sentinel lymph node biopsy (SLNB) for axillary staging for many patients. For example, the phase 3 randomized ACOSOG Z0011 trial showed that among women with T1/2 breast cancer, without palpable lymph nodes and one to two sentinel lymph nodes positive, survival outcomes were noninferior for sentinel lymph node dissection vs axillary lymph node dissection.¹ The SOUND (Sentinel Node vs Observation After Axillary Ultra-Sound) trial was a phase 3 prospective randomized study that included 1405 women with early breast cancer, tumor size ≤ 2 cm, and negative preoperative axillary ultrasound, and was designed to investigate the effect of axillary surgery omission in these patients (Gentilini et al). Five-year distant disease-free survival, the primary endpoint, was 97.7% in the SLNB group and 98.0% in the no-axillary-surgery group (log-rank P = .67; hazard ratio [HR] 0.84, noninferiority P = .02). Rates of locoregional relapse (1.7% vs 1.6%), distant metastases (1.8% vs 2.0%), and deaths (3.0% vs 2.6%) were similar in the SLNB group compared with the no-axillary-surgery group, respectively. Furthermore, adjuvant treatments were not significantly different between the two groups, indicating that tumor biology/genomics may have an expanding role in tailoring adjuvant therapy compared with clinicopathologic features. The results of this study suggest that axillary surgery omission can be considered in patients with ≤ T2 early breast cancer and negative axillary ultrasound when absence of this pathologic information does not affect the adjuvant treatment plan.

Hormone receptor–positive breast cancer is the most common subtype, with established risk factors including exposure to exogenous hormones, reproductive history, and lifestyle components (alcohol intake, obesity). There are also less-recognized environmental influences that may disrupt endocrine pathways and, as a result, affect tumor development. Fine particulate matter (PM_2.5), produced by combustion processes (vehicles, industrial facilities), burning wood, and fires, among other sources, is composed of various airborne pollutants (metals, organic compounds, ammonium, nitrate, ozone, sulfate, etc.). Prior studies evaluating the association of PM_2.5 and breast cancer development have shown mixed results.^3,4 A prospective US cohort study including 196,905 women without a prior history of breast cancer estimated historical annual average PM_2.5 concentrations between 1980 and 1984 (10 years prior to enrollment) (White et al). A total of 15,870 breast cancer cases were identified, and a 10 μg/m³ increase in PM_2.5 was associated with an 8% increase in overall breast cancer incidence (HR 1.08; 95% CI 1.02-1.13). The association was observed for estrogen-receptor (ER)-positive (HR 1.10; 95% CI 1.04-1.17) but not ER-negative tumors. Future studies focusing on historic exposures, investigating geographic differences and the resultant effect on cancer development, are of interest.

HER2CLIMB was a pivotal phase 3 randomized, double-blinded trial that demonstrated significant improvement in survival outcomes with the combination of tucatinib/trastuzumab/capecitabine vs tucatinib/trastuzumab/placebo among patients with previously treated human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer.⁵ Real-world data help inform our daily practice because patients enrolled in clinical trials do not always accurately represent the general population. A retrospective cohort study including 3449 patients with HER2-positive metastatic breast cancer evaluated outcomes with tucatinib in a real-world setting, demonstrating results similar to those seen in HER2CLIMB. Among all patients who received tucatinib (n = 216), median real-world time to treatment discontinuation was 6.5 months (95% CI 5.4-8.8), median real-world time to next treatment (which can serve as a proxy for progression-free survival) was 8.7 months (95% CI 6.8-10.7), and real-world overall survival was 26.6 months (95% CI 20.2–not reached). Median real-world time to treatment discontinuation was 8.1 months (95% CI 5.7-9.5) for patients who received the approved tucatinib triplet combination after one or more HER2-directed regimens in the metastatic setting and 9.4 months (95% CI 6.3-14.1) for those receiving it in the second- or third-line setting (Kaufman et al). These results support the efficacy of tucatinib in a real-world population, suggesting that earlier use (second or third line) may result in better outcomes. Future studies will continue to address the positioning of tucatinib in the treatment algorithm for HER2-positive metastatic breast cancer, including the evaluation of novel combinations.

Additional References

1. Giuliano AE et al. Effect of axillary dissection vs no axillary dissection on 10-year overall survival among women with invasive breast cancer and sentinel node metastasis: The ACOSOG Z0011 (Alliance) randomized clinical trial. JAMA. 2017;318:918-926. doi: 10.1001/jama.2017.11470 
2. Bartels SAL, Donker M, et al. Radiotherapy or surgery of the axilla after a positive sentinel node in breast cancer: 10-year results of the randomized controlled EORTC 10981-22023 AMAROS Trial. J Clin Oncol. 2023;41:2159-2165. doi: 10.1200/JCO.22.01565
3. Gabet S, Lemarchand C, Guénel P, Slama R. Breast cancer risk in association with atmospheric pollution exposure: A meta-analysis of effect estimates followed by a health impact assessment. Environ Health Perspect. 2021;129:57012. doi: 10.1289/EHP8419
4. Hvidtfeldt UA et al. Breast cancer incidence in relation to long-term low-level exposure to air pollution in the ELAPSE pooled cohort. Cancer Epidemiol Biomarkers Prev. 2023;32:105-113. doi: 10.1158/1055-9965.EPI-22-0720  
5. Murthy RK et al. Tucatinib, trastuzumab, and capecitabine for HER2-positive metastatic breast cancer. N Engl J Med. 2020;382:597-609. doi:10.1056/NEJMoa1914609