Jennifer A. DeSimone, MD

Cutaneous T-cell lymphoma (CTCL) is a diverse group of skin-homing T-cell neoplasms with a wide array of clinical presentations, immunohistopathologic subtypes, and prognoses. The age-adjusted incidence of CTCL in the United States is 6.4 per million individuals.¹ In the early stages of CTCL, the malignant lymphocytes are isolated to the skin, while more advanced disease involves metastatic spread to the lymphatic and peripheral blood compartments. Mycosis fungoides (MF) is the most common subtype of CTCL, comprising roughly 50% of all cases. The etiology of CTCL and MF remains poorly understood and no unifying driver mutation has been identified.² However, recent sequencing efforts have revealed recurrent genomics alterations primarily in 3 pathways: constitutive T-cell activation, resistance to apoptosis/cell-cycle dysregulation, and DNA structural/gene expression dysregulation.^3-8 These studies, among others, support the assertion that CTCL may be an epigenetic phenomenon.^9-14

Most patients with MF will experience an indolent course of skin-limited disease with a favorable prognosis and a 5-year survival rate of 88%.^15-17 A large study of patients with MF (N=525) followed for more than 40 years determined that approximately 20% of early-stage (IA-IIA) patients with MF progress to develop tumors, metastasis to the lymphatic tissue, and/or leukemic blood disease.¹⁸

Cutaneous T-cell lymphoma is a chronic disease, and most treatment responses are partial and short-lived. Allogenic hematopoietic transplantation is the only potentially curative option, and all other therapies are aimed at arresting progression and achieving remission.¹⁹ Skin-directed therapies include topical steroids, topical nitrogen mustard, phototherapy, and radiation. Systemic therapies such as oral retinoids, chemotherapy, and immunotherapy may be used alone or in combination with skin-directed therapies based on the overall disease stage and clinical presentation. Unfortunately, complete response (CR) to therapy is rare and fleeting, and most patients require multiple sequential treatments over their lifetimes.²⁰

Across all stages of CTCL, there is a therapeutic push to combination and immune-based therapies to achieve more durable responses. The imidazoquinolines are a family of toll-like receptor (TLR) agonists including imiquimod (TLR7) and resiquimod (TLR7 and TLR8). Imiquimod (IMQ) is a topical immunomodulator, which increases the local cytotoxic helper T-cell profile (T_H1 marked by IFN-α, tumor necrosis factor α, IL-1α, IL-6, and IL-8), thereby enhancing both humoral and innate immune responses targeting tumor cells.^21-23 Several small studies evaluating topical TLR agonists have documented efficacy in patients with early and advanced stages of CTCL.^24-34

Skin-directed chemotherapy using 5-fluorouracil (5-FU) has shown activity against many cutaneous malignancies. 5-Fluorouracil is an antimetabolite drug that inhibits thymidylate synthase, resulting in interrupted DNA and RNA synthesis and leading to an apoptotic cell death (Figure 1). It has been administered via intravenous, oral (prodrug), intralesional (IL), and topical routes with well-documented success in treating cutaneous squamous cell carcinoma, keratoacanthoma, basal cell carcinoma, and precancerous actinic keratosis.³⁵ As a topical, 5-FU has been shown to provide a good response in 6 patients with early MF.³⁶ In late-stage MF, 5-FU has been used in combination with methotrexate as an infusion.³⁷ We present a single-center case series of 9 patients with CTCL who received combination IL 5-FU and IMQ cream 5%.

Methods

Patient Selection—Patients were selected from our multidisciplinary CTCL subspecialty clinic at the Inova Schar Cancer Institute (Fairfax, Virginia). Patients with single to few recalcitrant CTCL plaques or tumors that were symptomatic or otherwise bothersome were included. All patients had at least 2 prior skin-directed therapies that failed, and many had advanced-stage disease requiring systemic therapy. All patients provided verbal consent.

Study Materials and Evaluations—Patients received IL injections of 5-FU 50 mg/mL. The volume injected was approximately 0.2 cc per cubic centimeter of lesion tissue. Injections were repeated at 2- to 3-week intervals until the target lesions achieved an acute hemorrhagic phase characterized by erosion, flattening, and crust formation. The total number of serial injections administered ranged from 1 to 5. The patients concomitantly treated all lesions with IMQ cream 5% daily for a duration of 2 to 3 months.

Medical photography and physical examination were performed every 2 to 3 weeks until the hemorrhagic phase resolved and treated sites re-epithelialized. Index lesions were assessed using the Composite Assessment of Index Lesion Severity (CAILS) score by a single investigator for all patients.³⁸ Scores were retrospectively assigned using the investigator’s detailed physical examination descriptions and extensive medical photography. Any hyperpigmentation was scored as residual disease, despite the fair interpretation of it as procedure-related postinflammatory dyspigmentation. Complete response was strictly defined as a CAILS score of 0. The patients were screened for possible systemic effects of IMQ, including the presence of fever, chills, fatigue, and myalgia. Patients were evaluated every 6 to 12 weeks as a standing follow-up.

Statistical Analysis—Reductions were calculated using local regression from baseline to the 4- to 7-week follow-up. Patients with multiple lesions had their CAILS score averaged at ea

Results

Nine patients aged 28 to 91 years (median age, 66 years) with CTCL stages IA to IVA2, who had lesions located throughout their body, achieved CR; 3 patients were female (Table 1). The most common phenotype was CD8⁺ (n=3). All patients had at least 2 prior skin-directed therapies at treatment sites that failed, and 1 patient had 7 prior treatments that failed. Prior treatments included a variety of modalities, including all standard-of-care options and enrollment in clinical trials. One patient died from pneumonia following CR (Table 2). Seven patients had previously received systemic therapy for CTCL, and 1 patient was stable on romidepsin during our study. In patients who received more than 1 injection of 5-FU—1 injection: 3 patients; 2 injections: 3 patients; 3 injections: 1 patient; 4 injections: 1 patient; 5 injections: 1 patient—injections were spaced by 2 to 3 weeks. There was 1 patient who initially had an inadequate dosing of IL 5-FU and was restarted 14 months later; this was the patient with 5 total injections. This occurred in one of the first patients in the study, who presented with a facial lesion. The investigator used approximately 0.02 cc per cubic centimeter (dose reduction of nearly 90%), which was inadequate and did not achieve the requisite hemorrhagic phase.

Treatment was well tolerated overall. In all cases, a hemorrhagic phase was achieved, characterized by erosion and crusting that was rated as mildly uncomfortable by 7 patients and moderately uncomfortable by 2 patients. In total, 15 lesions in all 9 patients achieved a CR within 24 weeks of the final injection. The longest treatment course required 12 weeks of therapy with IMQ and 5 IL injections of 5-FU. The fastest CR was achieved in patient 6 within 6 weeks following a single IL injection of 5-FU and 2 applications of IMQ. The average time to CR was 14.78 weeks (95% CI, 1.75-27.81)(Figure 2), and the time to CR ranged from 4 to 24 weeks. On average, patients achieved more than 50% reduction in CAILS score by 3.53 weeks (95% CI, 1.55-5.51) and nearly a 4-fold (74.7%) reduction at the time of initial follow-up (occurring at 4–7 weeks). By 7 weeks, patient 3 had the most modest improvement in CAILS score with a 2.75-fold reduction, while patient 5 had the largest decrease with a 5-fold reduction. Figure 3 shows representative clinical photographs of 2 patients before and after treatment, with all patients having similar results.

Comment

Cutaneous T-cell lymphoma is a chronic skin cancer with a pattern of limited response to therapy and frequent recurrence. Currently available skin-directed therapies function as temporizing measures rather than curative treatments. Immunotherapy offers the promise of lasting disease control even after cessation of treatment, as it may essentially awaken cutaneous immune surveillance to malignant lymphocytes.

Several small observational studies have evaluated topical IMQ and TLR agonist therapy in CTCL. The construct of prior reports varies widely, including many different pretreatments, dosing schemes, and follow-up periods.^24-33 Dosing intervals with IMQ ranged from daily to 3 times per week and treatment duration from 2 weeks to 1 year. Complete response rates from 50% to 100% were reported, and partial responses were observed in all but 1 patient, with recurrence-free follow-up ranging from 6 months to 8 years. Comparatively, combining IL 5-FU and IMQ appears to be at least as effective as IMQ alone or in other sequential treatments and combinations.^24-33

Resiquimod, an experimental TLR7/8 agonist, has shown promising results in CTCL. Rook et al³⁴ conducted a phase 1 trial of topical resiquimod in 12 early-stage patients with CTCL, all of whom responded to therapy. Two patients achieved CR, and 9 achieved a partial response, including 5 patients with the folliculotropic subtype. Interestingly, an abscopal effect was observed in 92% (11/12) of patients. Molecular evidence of reduction of the malignant clone was observed in 90% of patients via high-throughput sequencing of lesional tissue.³⁴ These exciting findings suggest that topical immune therapy with TLR agonists may achieve robust, sustained, and possibly global disease control in CTCL.

Topical therapies are limited by depth of absorption, which can present a barrier to using these treatments for thicker plaques and tumors. Combining IL and topical routes was critical in our study design. Having good clinical experience using IL 5-FU in nonmelanoma skin cancers, we hypothesized that IL 5-FU would achieve a cytotoxic response through the full depth of thicker lesions and erode the surface of these lesions to facilitate penetration of topical IMQ. We additionally hypothesized that the combination of mechanisms of action would lead to an additive or synergistic response (Figure 1). By first inducing apoptotic cell death via 5-FU, we hoped to spill malignant lymphocyte neoantigens. Coupling that antigen exposure with an enhanced T_H1-biased immune response driven by IMQ should facilitate tumor clearance and immune education against malignant T cells.

In our case series, all 15 lesions in 9 patients completely cleared, and no recurrences were observed at 26-month follow-up. No patients encountered any major adverse events, and the procedure was well tolerated by all.

Study Limitations—Limitations of this small study certainly exist. It is impossible to prove that our mechanistic theory is accurate given our strictly clinical assessment tools. We speculate that if our results had been achieved with IL 5-FU alone, future investigation with a prospective study using multiple treatment arms including a control would be warranted. Kannangara et al³⁶ reported the use of topical 5-FU for MF and the drug’s utility in either topical or IL routes for CTCL, which deserves further study. It is less likely that results were achieved exclusively by IMQ because of the rapid tissue breakdown observed in the acute hemorrhagic phase. This phenomenon is best explained by the sudden apoptosis caused by DNA intercalation from 5-FU. The follow-up period is not uniform because this was a rolling enrollment study. Follow-up will be ongoing, and we aim to assess all patients up to at least the 5-year point. A final limitation of this study is the purely clinical end point. In the future, pretreatment and posttreatment biopsies would be useful in assessing proof of histologic response, and high-throughput sequencing may be used to look for molecular clearance via liquid biopsy. Lastly, careful observation for possible abscopal effect using the Severity-Weighted Assessment Tool score would be interesting and potentially contributory to our understanding of the impact of topical immune therapy on cutaneous tumor surveillance.

Conclusion

Combination IL 5-FU and topical IMQ is a well-tolerated, effective, and durable therapy for recalcitrant thick plaques and tumors of CTCL. This treatment is convenient and cost-effective. The procedure is performed in less than 5 minutes in an outpatient dermatology clinic. All patients received full insurance coverage for both drug and procedure fees under Medicare and commercial carriers.

Cutaneous T-cell lymphoma (CTCL) is a diverse group of skin-homing T-cell neoplasms with a wide array of clinical presentations, immunohistopathologic subtypes, and prognoses. The age-adjusted incidence of CTCL in the United States is 6.4 per million individuals.¹ In the early stages of CTCL, the malignant lymphocytes are isolated to the skin, while more advanced disease involves metastatic spread to the lymphatic and peripheral blood compartments. Mycosis fungoides (MF) is the most common subtype of CTCL, comprising roughly 50% of all cases. The etiology of CTCL and MF remains poorly understood and no unifying driver mutation has been identified.² However, recent sequencing efforts have revealed recurrent genomics alterations primarily in 3 pathways: constitutive T-cell activation, resistance to apoptosis/cell-cycle dysregulation, and DNA structural/gene expression dysregulation.^3-8 These studies, among others, support the assertion that CTCL may be an epigenetic phenomenon.^9-14

Most patients with MF will experience an indolent course of skin-limited disease with a favorable prognosis and a 5-year survival rate of 88%.^15-17 A large study of patients with MF (N=525) followed for more than 40 years determined that approximately 20% of early-stage (IA-IIA) patients with MF progress to develop tumors, metastasis to the lymphatic tissue, and/or leukemic blood disease.¹⁸

Cutaneous T-cell lymphoma is a chronic disease, and most treatment responses are partial and short-lived. Allogenic hematopoietic transplantation is the only potentially curative option, and all other therapies are aimed at arresting progression and achieving remission.¹⁹ Skin-directed therapies include topical steroids, topical nitrogen mustard, phototherapy, and radiation. Systemic therapies such as oral retinoids, chemotherapy, and immunotherapy may be used alone or in combination with skin-directed therapies based on the overall disease stage and clinical presentation. Unfortunately, complete response (CR) to therapy is rare and fleeting, and most patients require multiple sequential treatments over their lifetimes.²⁰

Across all stages of CTCL, there is a therapeutic push to combination and immune-based therapies to achieve more durable responses. The imidazoquinolines are a family of toll-like receptor (TLR) agonists including imiquimod (TLR7) and resiquimod (TLR7 and TLR8). Imiquimod (IMQ) is a topical immunomodulator, which increases the local cytotoxic helper T-cell profile (T_H1 marked by IFN-α, tumor necrosis factor α, IL-1α, IL-6, and IL-8), thereby enhancing both humoral and innate immune responses targeting tumor cells.^21-23 Several small studies evaluating topical TLR agonists have documented efficacy in patients with early and advanced stages of CTCL.^24-34

Skin-directed chemotherapy using 5-fluorouracil (5-FU) has shown activity against many cutaneous malignancies. 5-Fluorouracil is an antimetabolite drug that inhibits thymidylate synthase, resulting in interrupted DNA and RNA synthesis and leading to an apoptotic cell death (Figure 1). It has been administered via intravenous, oral (prodrug), intralesional (IL), and topical routes with well-documented success in treating cutaneous squamous cell carcinoma, keratoacanthoma, basal cell carcinoma, and precancerous actinic keratosis.³⁵ As a topical, 5-FU has been shown to provide a good response in 6 patients with early MF.³⁶ In late-stage MF, 5-FU has been used in combination with methotrexate as an infusion.³⁷ We present a single-center case series of 9 patients with CTCL who received combination IL 5-FU and IMQ cream 5%.

Methods

Patient Selection—Patients were selected from our multidisciplinary CTCL subspecialty clinic at the Inova Schar Cancer Institute (Fairfax, Virginia). Patients with single to few recalcitrant CTCL plaques or tumors that were symptomatic or otherwise bothersome were included. All patients had at least 2 prior skin-directed therapies that failed, and many had advanced-stage disease requiring systemic therapy. All patients provided verbal consent.

Study Materials and Evaluations—Patients received IL injections of 5-FU 50 mg/mL. The volume injected was approximately 0.2 cc per cubic centimeter of lesion tissue. Injections were repeated at 2- to 3-week intervals until the target lesions achieved an acute hemorrhagic phase characterized by erosion, flattening, and crust formation. The total number of serial injections administered ranged from 1 to 5. The patients concomitantly treated all lesions with IMQ cream 5% daily for a duration of 2 to 3 months.

Medical photography and physical examination were performed every 2 to 3 weeks until the hemorrhagic phase resolved and treated sites re-epithelialized. Index lesions were assessed using the Composite Assessment of Index Lesion Severity (CAILS) score by a single investigator for all patients.³⁸ Scores were retrospectively assigned using the investigator’s detailed physical examination descriptions and extensive medical photography. Any hyperpigmentation was scored as residual disease, despite the fair interpretation of it as procedure-related postinflammatory dyspigmentation. Complete response was strictly defined as a CAILS score of 0. The patients were screened for possible systemic effects of IMQ, including the presence of fever, chills, fatigue, and myalgia. Patients were evaluated every 6 to 12 weeks as a standing follow-up.

Statistical Analysis—Reductions were calculated using local regression from baseline to the 4- to 7-week follow-up. Patients with multiple lesions had their CAILS score averaged at ea

Results

Nine patients aged 28 to 91 years (median age, 66 years) with CTCL stages IA to IVA2, who had lesions located throughout their body, achieved CR; 3 patients were female (Table 1). The most common phenotype was CD8⁺ (n=3). All patients had at least 2 prior skin-directed therapies at treatment sites that failed, and 1 patient had 7 prior treatments that failed. Prior treatments included a variety of modalities, including all standard-of-care options and enrollment in clinical trials. One patient died from pneumonia following CR (Table 2). Seven patients had previously received systemic therapy for CTCL, and 1 patient was stable on romidepsin during our study. In patients who received more than 1 injection of 5-FU—1 injection: 3 patients; 2 injections: 3 patients; 3 injections: 1 patient; 4 injections: 1 patient; 5 injections: 1 patient—injections were spaced by 2 to 3 weeks. There was 1 patient who initially had an inadequate dosing of IL 5-FU and was restarted 14 months later; this was the patient with 5 total injections. This occurred in one of the first patients in the study, who presented with a facial lesion. The investigator used approximately 0.02 cc per cubic centimeter (dose reduction of nearly 90%), which was inadequate and did not achieve the requisite hemorrhagic phase.

Treatment was well tolerated overall. In all cases, a hemorrhagic phase was achieved, characterized by erosion and crusting that was rated as mildly uncomfortable by 7 patients and moderately uncomfortable by 2 patients. In total, 15 lesions in all 9 patients achieved a CR within 24 weeks of the final injection. The longest treatment course required 12 weeks of therapy with IMQ and 5 IL injections of 5-FU. The fastest CR was achieved in patient 6 within 6 weeks following a single IL injection of 5-FU and 2 applications of IMQ. The average time to CR was 14.78 weeks (95% CI, 1.75-27.81)(Figure 2), and the time to CR ranged from 4 to 24 weeks. On average, patients achieved more than 50% reduction in CAILS score by 3.53 weeks (95% CI, 1.55-5.51) and nearly a 4-fold (74.7%) reduction at the time of initial follow-up (occurring at 4–7 weeks). By 7 weeks, patient 3 had the most modest improvement in CAILS score with a 2.75-fold reduction, while patient 5 had the largest decrease with a 5-fold reduction. Figure 3 shows representative clinical photographs of 2 patients before and after treatment, with all patients having similar results.

Comment

Cutaneous T-cell lymphoma is a chronic skin cancer with a pattern of limited response to therapy and frequent recurrence. Currently available skin-directed therapies function as temporizing measures rather than curative treatments. Immunotherapy offers the promise of lasting disease control even after cessation of treatment, as it may essentially awaken cutaneous immune surveillance to malignant lymphocytes.

Several small observational studies have evaluated topical IMQ and TLR agonist therapy in CTCL. The construct of prior reports varies widely, including many different pretreatments, dosing schemes, and follow-up periods.^24-33 Dosing intervals with IMQ ranged from daily to 3 times per week and treatment duration from 2 weeks to 1 year. Complete response rates from 50% to 100% were reported, and partial responses were observed in all but 1 patient, with recurrence-free follow-up ranging from 6 months to 8 years. Comparatively, combining IL 5-FU and IMQ appears to be at least as effective as IMQ alone or in other sequential treatments and combinations.^24-33

Resiquimod, an experimental TLR7/8 agonist, has shown promising results in CTCL. Rook et al³⁴ conducted a phase 1 trial of topical resiquimod in 12 early-stage patients with CTCL, all of whom responded to therapy. Two patients achieved CR, and 9 achieved a partial response, including 5 patients with the folliculotropic subtype. Interestingly, an abscopal effect was observed in 92% (11/12) of patients. Molecular evidence of reduction of the malignant clone was observed in 90% of patients via high-throughput sequencing of lesional tissue.³⁴ These exciting findings suggest that topical immune therapy with TLR agonists may achieve robust, sustained, and possibly global disease control in CTCL.

Topical therapies are limited by depth of absorption, which can present a barrier to using these treatments for thicker plaques and tumors. Combining IL and topical routes was critical in our study design. Having good clinical experience using IL 5-FU in nonmelanoma skin cancers, we hypothesized that IL 5-FU would achieve a cytotoxic response through the full depth of thicker lesions and erode the surface of these lesions to facilitate penetration of topical IMQ. We additionally hypothesized that the combination of mechanisms of action would lead to an additive or synergistic response (Figure 1). By first inducing apoptotic cell death via 5-FU, we hoped to spill malignant lymphocyte neoantigens. Coupling that antigen exposure with an enhanced T_H1-biased immune response driven by IMQ should facilitate tumor clearance and immune education against malignant T cells.

In our case series, all 15 lesions in 9 patients completely cleared, and no recurrences were observed at 26-month follow-up. No patients encountered any major adverse events, and the procedure was well tolerated by all.

Study Limitations—Limitations of this small study certainly exist. It is impossible to prove that our mechanistic theory is accurate given our strictly clinical assessment tools. We speculate that if our results had been achieved with IL 5-FU alone, future investigation with a prospective study using multiple treatment arms including a control would be warranted. Kannangara et al³⁶ reported the use of topical 5-FU for MF and the drug’s utility in either topical or IL routes for CTCL, which deserves further study. It is less likely that results were achieved exclusively by IMQ because of the rapid tissue breakdown observed in the acute hemorrhagic phase. This phenomenon is best explained by the sudden apoptosis caused by DNA intercalation from 5-FU. The follow-up period is not uniform because this was a rolling enrollment study. Follow-up will be ongoing, and we aim to assess all patients up to at least the 5-year point. A final limitation of this study is the purely clinical end point. In the future, pretreatment and posttreatment biopsies would be useful in assessing proof of histologic response, and high-throughput sequencing may be used to look for molecular clearance via liquid biopsy. Lastly, careful observation for possible abscopal effect using the Severity-Weighted Assessment Tool score would be interesting and potentially contributory to our understanding of the impact of topical immune therapy on cutaneous tumor surveillance.

Conclusion

Combination IL 5-FU and topical IMQ is a well-tolerated, effective, and durable therapy for recalcitrant thick plaques and tumors of CTCL. This treatment is convenient and cost-effective. The procedure is performed in less than 5 minutes in an outpatient dermatology clinic. All patients received full insurance coverage for both drug and procedure fees under Medicare and commercial carriers.

Cutaneous T-cell lymphoma (CTCL) is a diverse group of skin-homing T-cell neoplasms with a wide array of clinical presentations, immunohistopathologic subtypes, and prognoses. The age-adjusted incidence of CTCL in the United States is 6.4 per million individuals.¹ In the early stages of CTCL, the malignant lymphocytes are isolated to the skin, while more advanced disease involves metastatic spread to the lymphatic and peripheral blood compartments. Mycosis fungoides (MF) is the most common subtype of CTCL, comprising roughly 50% of all cases. The etiology of CTCL and MF remains poorly understood and no unifying driver mutation has been identified.² However, recent sequencing efforts have revealed recurrent genomics alterations primarily in 3 pathways: constitutive T-cell activation, resistance to apoptosis/cell-cycle dysregulation, and DNA structural/gene expression dysregulation.^3-8 These studies, among others, support the assertion that CTCL may be an epigenetic phenomenon.^9-14

Most patients with MF will experience an indolent course of skin-limited disease with a favorable prognosis and a 5-year survival rate of 88%.^15-17 A large study of patients with MF (N=525) followed for more than 40 years determined that approximately 20% of early-stage (IA-IIA) patients with MF progress to develop tumors, metastasis to the lymphatic tissue, and/or leukemic blood disease.¹⁸

Cutaneous T-cell lymphoma is a chronic disease, and most treatment responses are partial and short-lived. Allogenic hematopoietic transplantation is the only potentially curative option, and all other therapies are aimed at arresting progression and achieving remission.¹⁹ Skin-directed therapies include topical steroids, topical nitrogen mustard, phototherapy, and radiation. Systemic therapies such as oral retinoids, chemotherapy, and immunotherapy may be used alone or in combination with skin-directed therapies based on the overall disease stage and clinical presentation. Unfortunately, complete response (CR) to therapy is rare and fleeting, and most patients require multiple sequential treatments over their lifetimes.²⁰

Across all stages of CTCL, there is a therapeutic push to combination and immune-based therapies to achieve more durable responses. The imidazoquinolines are a family of toll-like receptor (TLR) agonists including imiquimod (TLR7) and resiquimod (TLR7 and TLR8). Imiquimod (IMQ) is a topical immunomodulator, which increases the local cytotoxic helper T-cell profile (T_H1 marked by IFN-α, tumor necrosis factor α, IL-1α, IL-6, and IL-8), thereby enhancing both humoral and innate immune responses targeting tumor cells.^21-23 Several small studies evaluating topical TLR agonists have documented efficacy in patients with early and advanced stages of CTCL.^24-34

Skin-directed chemotherapy using 5-fluorouracil (5-FU) has shown activity against many cutaneous malignancies. 5-Fluorouracil is an antimetabolite drug that inhibits thymidylate synthase, resulting in interrupted DNA and RNA synthesis and leading to an apoptotic cell death (Figure 1). It has been administered via intravenous, oral (prodrug), intralesional (IL), and topical routes with well-documented success in treating cutaneous squamous cell carcinoma, keratoacanthoma, basal cell carcinoma, and precancerous actinic keratosis.³⁵ As a topical, 5-FU has been shown to provide a good response in 6 patients with early MF.³⁶ In late-stage MF, 5-FU has been used in combination with methotrexate as an infusion.³⁷ We present a single-center case series of 9 patients with CTCL who received combination IL 5-FU and IMQ cream 5%.

Methods

Patient Selection—Patients were selected from our multidisciplinary CTCL subspecialty clinic at the Inova Schar Cancer Institute (Fairfax, Virginia). Patients with single to few recalcitrant CTCL plaques or tumors that were symptomatic or otherwise bothersome were included. All patients had at least 2 prior skin-directed therapies that failed, and many had advanced-stage disease requiring systemic therapy. All patients provided verbal consent.

Study Materials and Evaluations—Patients received IL injections of 5-FU 50 mg/mL. The volume injected was approximately 0.2 cc per cubic centimeter of lesion tissue. Injections were repeated at 2- to 3-week intervals until the target lesions achieved an acute hemorrhagic phase characterized by erosion, flattening, and crust formation. The total number of serial injections administered ranged from 1 to 5. The patients concomitantly treated all lesions with IMQ cream 5% daily for a duration of 2 to 3 months.

Medical photography and physical examination were performed every 2 to 3 weeks until the hemorrhagic phase resolved and treated sites re-epithelialized. Index lesions were assessed using the Composite Assessment of Index Lesion Severity (CAILS) score by a single investigator for all patients.³⁸ Scores were retrospectively assigned using the investigator’s detailed physical examination descriptions and extensive medical photography. Any hyperpigmentation was scored as residual disease, despite the fair interpretation of it as procedure-related postinflammatory dyspigmentation. Complete response was strictly defined as a CAILS score of 0. The patients were screened for possible systemic effects of IMQ, including the presence of fever, chills, fatigue, and myalgia. Patients were evaluated every 6 to 12 weeks as a standing follow-up.

Statistical Analysis—Reductions were calculated using local regression from baseline to the 4- to 7-week follow-up. Patients with multiple lesions had their CAILS score averaged at ea

Results

Nine patients aged 28 to 91 years (median age, 66 years) with CTCL stages IA to IVA2, who had lesions located throughout their body, achieved CR; 3 patients were female (Table 1). The most common phenotype was CD8⁺ (n=3). All patients had at least 2 prior skin-directed therapies at treatment sites that failed, and 1 patient had 7 prior treatments that failed. Prior treatments included a variety of modalities, including all standard-of-care options and enrollment in clinical trials. One patient died from pneumonia following CR (Table 2). Seven patients had previously received systemic therapy for CTCL, and 1 patient was stable on romidepsin during our study. In patients who received more than 1 injection of 5-FU—1 injection: 3 patients; 2 injections: 3 patients; 3 injections: 1 patient; 4 injections: 1 patient; 5 injections: 1 patient—injections were spaced by 2 to 3 weeks. There was 1 patient who initially had an inadequate dosing of IL 5-FU and was restarted 14 months later; this was the patient with 5 total injections. This occurred in one of the first patients in the study, who presented with a facial lesion. The investigator used approximately 0.02 cc per cubic centimeter (dose reduction of nearly 90%), which was inadequate and did not achieve the requisite hemorrhagic phase.

Treatment was well tolerated overall. In all cases, a hemorrhagic phase was achieved, characterized by erosion and crusting that was rated as mildly uncomfortable by 7 patients and moderately uncomfortable by 2 patients. In total, 15 lesions in all 9 patients achieved a CR within 24 weeks of the final injection. The longest treatment course required 12 weeks of therapy with IMQ and 5 IL injections of 5-FU. The fastest CR was achieved in patient 6 within 6 weeks following a single IL injection of 5-FU and 2 applications of IMQ. The average time to CR was 14.78 weeks (95% CI, 1.75-27.81)(Figure 2), and the time to CR ranged from 4 to 24 weeks. On average, patients achieved more than 50% reduction in CAILS score by 3.53 weeks (95% CI, 1.55-5.51) and nearly a 4-fold (74.7%) reduction at the time of initial follow-up (occurring at 4–7 weeks). By 7 weeks, patient 3 had the most modest improvement in CAILS score with a 2.75-fold reduction, while patient 5 had the largest decrease with a 5-fold reduction. Figure 3 shows representative clinical photographs of 2 patients before and after treatment, with all patients having similar results.

Comment

Cutaneous T-cell lymphoma is a chronic skin cancer with a pattern of limited response to therapy and frequent recurrence. Currently available skin-directed therapies function as temporizing measures rather than curative treatments. Immunotherapy offers the promise of lasting disease control even after cessation of treatment, as it may essentially awaken cutaneous immune surveillance to malignant lymphocytes.

Several small observational studies have evaluated topical IMQ and TLR agonist therapy in CTCL. The construct of prior reports varies widely, including many different pretreatments, dosing schemes, and follow-up periods.^24-33 Dosing intervals with IMQ ranged from daily to 3 times per week and treatment duration from 2 weeks to 1 year. Complete response rates from 50% to 100% were reported, and partial responses were observed in all but 1 patient, with recurrence-free follow-up ranging from 6 months to 8 years. Comparatively, combining IL 5-FU and IMQ appears to be at least as effective as IMQ alone or in other sequential treatments and combinations.^24-33

Resiquimod, an experimental TLR7/8 agonist, has shown promising results in CTCL. Rook et al³⁴ conducted a phase 1 trial of topical resiquimod in 12 early-stage patients with CTCL, all of whom responded to therapy. Two patients achieved CR, and 9 achieved a partial response, including 5 patients with the folliculotropic subtype. Interestingly, an abscopal effect was observed in 92% (11/12) of patients. Molecular evidence of reduction of the malignant clone was observed in 90% of patients via high-throughput sequencing of lesional tissue.³⁴ These exciting findings suggest that topical immune therapy with TLR agonists may achieve robust, sustained, and possibly global disease control in CTCL.

Topical therapies are limited by depth of absorption, which can present a barrier to using these treatments for thicker plaques and tumors. Combining IL and topical routes was critical in our study design. Having good clinical experience using IL 5-FU in nonmelanoma skin cancers, we hypothesized that IL 5-FU would achieve a cytotoxic response through the full depth of thicker lesions and erode the surface of these lesions to facilitate penetration of topical IMQ. We additionally hypothesized that the combination of mechanisms of action would lead to an additive or synergistic response (Figure 1). By first inducing apoptotic cell death via 5-FU, we hoped to spill malignant lymphocyte neoantigens. Coupling that antigen exposure with an enhanced T_H1-biased immune response driven by IMQ should facilitate tumor clearance and immune education against malignant T cells.

In our case series, all 15 lesions in 9 patients completely cleared, and no recurrences were observed at 26-month follow-up. No patients encountered any major adverse events, and the procedure was well tolerated by all.

Study Limitations—Limitations of this small study certainly exist. It is impossible to prove that our mechanistic theory is accurate given our strictly clinical assessment tools. We speculate that if our results had been achieved with IL 5-FU alone, future investigation with a prospective study using multiple treatment arms including a control would be warranted. Kannangara et al³⁶ reported the use of topical 5-FU for MF and the drug’s utility in either topical or IL routes for CTCL, which deserves further study. It is less likely that results were achieved exclusively by IMQ because of the rapid tissue breakdown observed in the acute hemorrhagic phase. This phenomenon is best explained by the sudden apoptosis caused by DNA intercalation from 5-FU. The follow-up period is not uniform because this was a rolling enrollment study. Follow-up will be ongoing, and we aim to assess all patients up to at least the 5-year point. A final limitation of this study is the purely clinical end point. In the future, pretreatment and posttreatment biopsies would be useful in assessing proof of histologic response, and high-throughput sequencing may be used to look for molecular clearance via liquid biopsy. Lastly, careful observation for possible abscopal effect using the Severity-Weighted Assessment Tool score would be interesting and potentially contributory to our understanding of the impact of topical immune therapy on cutaneous tumor surveillance.

Conclusion

Combination IL 5-FU and topical IMQ is a well-tolerated, effective, and durable therapy for recalcitrant thick plaques and tumors of CTCL. This treatment is convenient and cost-effective. The procedure is performed in less than 5 minutes in an outpatient dermatology clinic. All patients received full insurance coverage for both drug and procedure fees under Medicare and commercial carriers.

Systemic mastocytosis is a heterogeneous disorder of stem cell origin defined by abnormal hyperplasia and accumulation of mast cells (MCs) in one or more tissues.^1,2 The most commonly affected tissues are the bone marrow, gastrointestinal tract, and skin. Based on a number of major and minor criteria defined by the World Health Organization (WHO), the mastocytoses are subdivided into 7 variants that range from isolated cutaneous involvement to widespread systemic disease.^1-4 The most frequently diagnosed subtype is indolent systemic mastocytosis (ISM), a chronic disorder characterized by diffuse cutaneous macules and papules as well as bone marrow involvement in the form of multifocal dense infiltrates of MCs that frequently are phenotypically positive for c-KIT and tryptase. Serum tryptase levels are nearly invariably elevated in patients with this condition.^1,2

Symptoms of ISM are determined by the intermittent release of histamine and leukotrienes from hyperproliferating MCs as well as IL-6 and eosinophil chemotactic factors. As the burden of MC secretory products increases, patients experience worsening pruritus, flushing, palpitations, vomiting, and anaphylaxis in severe instances.^1,2,5 The mainstay of treatment of this condition involves symptom control through the inhibition of MC mediators.¹ The majority of patients respond well to antihistamines, antileukotriene agents, and oral corticosteroids during severe episodes of MC degranulation.^1,2,5

Unfortunately, some patients are unable to achieve adequate symptom control through the use of mediator-targeting treatments alone. In these cases, physicians often are faced with the following treatment dilemma: Either attempt to use therapies such as interferon alfa, which is cytoreductive to MCs, or 2-chlorodeoxyadenosine to reduce the overall MC burden, or turn to newer nonimmunosuppressive second-line options. We present the case of a patient with chronic ISM with progressive cutaneous lesions and poorly controlled pruritus that was previously managed with topical corticosteroids and antihistamines who responded favorably to treatment with narrowband UVB (NB-UVB) phototherapy.

Case Report

A 57-year-old woman presented with a 10-year history of widespread red-brown macules and papules on the trunk and upper and lower extremities. The lesions were intermittently pruritic, a symptom that was exacerbated on sun and heat exposure. A skin biopsy performed by an outside dermatologist 9 years prior confirmed the presence of mastocytosis. The patient was originally treated with triamcinolone cream and oral antihistamines, which controlled her symptoms successfully for nearly a decade.

At the current presentation, the patient reported increasingly severe pruritus and lesional spread to the neck and face of 15 months’ duration. She denied any symptoms of flushing, diarrhea, syncopal episodes, or lightheadedness. Physical examination revealed a well-appearing middle-aged woman with multiple 3- to 8-mm, red-brown, blanchable macules and papules with areas coalescing into plaques that primarily involved the legs (Figure 1A); arms; back; and to a lesser extent the abdomen, neck, and face. There was no palpable lymphadenopathy.

Laboratory results revealed a complete blood cell count and basic metabolic profile within reference range; however, the serum tryptase level was elevated at 65 ng/mL (reference range, <11.4 ng/mL). A positron emission tomography–computed tomography scan was negative, as well as a c-KIT mutation analysis. A review of the skin biopsy from 9 years prior demonstrated slight acanthosis with dermal proliferation of mononuclear cells (Figure 2A), some of which had abundant cytoplasm and oval-shaped nuclei. There were few eosinophils and marked dermal telangiectasias. Giemsa stain revealed increased numbers of MCs in the upper dermis (Figure 2B). A bone marrow biopsy performed 9 years later showed multifocal lesions composed of MCs with associated lymphoid aggregates without notable myelodyspoiesis (or myeloproliferative neoplasm). These features were all consistent with WHO criteria for ISM. Based on the most current clinical, laboratory, and histopathologic findings, the patient was diagnosed with category IB ISM.

The patient’s symptoms had remained stable for 9 years with a regimen of triamcinolone cream 0.1% twice daily, doxepin cream 5% daily as needed, and oral fexofenadine 180 mg once daily. The patient continues to use topical steroids and oral antihistamines. Due to inadequate symptom control, breakthrough pruritus, and the development of new skin lesions on the head and neck, she was started on NB-UVB treatment 2 months after presentation. The patient’s symptoms and the extent of cutaneous maculopapular lesions improved after 20 light treatments (Figure 1B), with even more dramatic results after 40 cycles of therapy (Figure 1C). Overall, the lower legs have proved most recalcitrant to this treatment modality. She is currently continuing to receive NB-UVB treatment twice weekly.

Comment

Systemic mastocytosis is a heterogeneous disorder characterized by the proliferation and accumulation of atypical MCs in tissues, principally in the bone marrow and skin, though involvement of the gastrointestinal tract, liver, spleen, and lymphatic system also have been reported.^1,2,6 The WHO classification of mastocytosis divides this condition into 7 subtypes.⁴ Indolent systemic mastocytosis is the most common variant.^2,6 The etiology of ISM is not fully understood, but there is evidence suggesting that an activating mutation of KIT proto-oncogene receptor tyrosine kinase, KIT (usually D816V), present in the MCs of nearly 80% of patients with ISM may be involved.^1,3-5,7 Patients occasionally present with predominantly cutaneous findings but typically seek medical attention due to the recurrent systemic symptoms of the disease (eg, pruritus, flushing, syncope, palpitations, headache, dyspepsia, vomiting, diarrhea), which are related to the release of MC mediators.^1,2

The management of ISM is complex and based primarily on symptom reduction without alteration of disease course.^1,2,5,7 Patients should avoid symptom triggers such as heat, humidity, emotional and physical stress, alcohol, and certain medications (ie, aspirin, opioids, radiocontrast agents).⁷ Patients are initially treated with histamine H1- and H2-receptor antagonists to alleviate MC mediator release symptoms.^1,2,8 Although H1 blockers are most effective in mitigating cutaneous symptoms and limiting pruritus, H2 blockers are used to control gastric hypersecretion and dyspepsia.² Proton pump inhibitors are useful in patients with peptic ulcer disease who are unresponsive to H2-receptor antagonist therapy.^2,7 Cromolyn sodium and ketotifen fumarate are MC stabilizers that help prevent degranulation, which is helpful in relieving most major ISM symptoms. Leukotriene antagonists, such as zafirlukast, montelukast sodium, or zileuton, also may be employed to target the proinflammatory and pruritogenic leukotrienes, also products of the MC protein.^2,7 Imatinib mesylate and masitinib mesylate, both tyrosine kinase inhibitors, have been shown to improve symptoms and reduce MC mediator levels in ISM; however, most patients harbor the resistant KIT D816V mutation, which limits the utility of this medication.Patients with sensitive KIT mutations or those who have the wild-type KIT D816 mutation may be more appropriate candidates for imatinib or masitinib therapy, which can ameliorate symptoms of flushing, pruritus, and depression.^7-10 Treatment with omalizumab, a humanized murine anti-IgE monoclonal antibody, can be effective in treating recurrent, treatment-refractory anaphylaxis in ISM patients.^5,7

Symptoms unresponsive to these therapies can be effectively treated with a short course of oral corticosteroids,^6,7 while MC cytoreductive therapies such as interferon alfa or 2-chlorodeoxyadenosine (cladribine/2-CdA) are reserved for refractory cases.^2,7 Alternative therapies such as NB-UVB² or psoralen plus UVA phototherapy¹¹ also have demonstrated success in treating ISM symptoms. In the past, NB-UVB has shown efficacy in controlling pruriginous conditions ranging from chronic urticaria^12,13 to atopic dermatitis¹⁴ to psoriasis.¹⁵ This evidence has spurred studies to evaluate if NB-UVB has a role in the management of uncontrolled cases of cutaneous and ISM.^2,13,16,17 To date, the evidence has been promising. The majority of patients treated with this regimen report subjective reduction in pruritus in addition to clinical cutaneous disease burden.^2,11 Also, laboratory analysis demonstrates decreased levels of tryptase in patients utilizing NB-UVB phototherapy.² Thus far, the use of NB-UVB phototherapy in the treatment of pruriginous disorders such as ISM has not been associated with any severe side effects such as increased rates of anaphylaxis, though some research has suggested that this therapy may lower the threshold for patients to develop symptomatic dermographism.¹² Overall, patients treated with NB-UVB phototherapy report improved quality of life related to more effective symptom control.¹⁶

Although ISM is currently considered an incurable chronic condition,⁶ this case illustrates that symptomatic management is possible, even in cases of long-standing, severe disease. Patients should still be encouraged to avoid triggering factors and be vigilant in preventing potential anaphylaxis. However, NB-UVB phototherapy provides a supplemental or alternative treatment choice when other therapies have failed. We hope that the success of NB-UVB demonstrated in this case provides further evidence that this light-based therapy is a valuable treatment option in mastocytosis patients with unremitting or poorly controlled symptoms.

Systemic mastocytosis is a heterogeneous disorder of stem cell origin defined by abnormal hyperplasia and accumulation of mast cells (MCs) in one or more tissues.^1,2 The most commonly affected tissues are the bone marrow, gastrointestinal tract, and skin. Based on a number of major and minor criteria defined by the World Health Organization (WHO), the mastocytoses are subdivided into 7 variants that range from isolated cutaneous involvement to widespread systemic disease.^1-4 The most frequently diagnosed subtype is indolent systemic mastocytosis (ISM), a chronic disorder characterized by diffuse cutaneous macules and papules as well as bone marrow involvement in the form of multifocal dense infiltrates of MCs that frequently are phenotypically positive for c-KIT and tryptase. Serum tryptase levels are nearly invariably elevated in patients with this condition.^1,2

Symptoms of ISM are determined by the intermittent release of histamine and leukotrienes from hyperproliferating MCs as well as IL-6 and eosinophil chemotactic factors. As the burden of MC secretory products increases, patients experience worsening pruritus, flushing, palpitations, vomiting, and anaphylaxis in severe instances.^1,2,5 The mainstay of treatment of this condition involves symptom control through the inhibition of MC mediators.¹ The majority of patients respond well to antihistamines, antileukotriene agents, and oral corticosteroids during severe episodes of MC degranulation.^1,2,5

Unfortunately, some patients are unable to achieve adequate symptom control through the use of mediator-targeting treatments alone. In these cases, physicians often are faced with the following treatment dilemma: Either attempt to use therapies such as interferon alfa, which is cytoreductive to MCs, or 2-chlorodeoxyadenosine to reduce the overall MC burden, or turn to newer nonimmunosuppressive second-line options. We present the case of a patient with chronic ISM with progressive cutaneous lesions and poorly controlled pruritus that was previously managed with topical corticosteroids and antihistamines who responded favorably to treatment with narrowband UVB (NB-UVB) phototherapy.

Case Report

A 57-year-old woman presented with a 10-year history of widespread red-brown macules and papules on the trunk and upper and lower extremities. The lesions were intermittently pruritic, a symptom that was exacerbated on sun and heat exposure. A skin biopsy performed by an outside dermatologist 9 years prior confirmed the presence of mastocytosis. The patient was originally treated with triamcinolone cream and oral antihistamines, which controlled her symptoms successfully for nearly a decade.

At the current presentation, the patient reported increasingly severe pruritus and lesional spread to the neck and face of 15 months’ duration. She denied any symptoms of flushing, diarrhea, syncopal episodes, or lightheadedness. Physical examination revealed a well-appearing middle-aged woman with multiple 3- to 8-mm, red-brown, blanchable macules and papules with areas coalescing into plaques that primarily involved the legs (Figure 1A); arms; back; and to a lesser extent the abdomen, neck, and face. There was no palpable lymphadenopathy.

Laboratory results revealed a complete blood cell count and basic metabolic profile within reference range; however, the serum tryptase level was elevated at 65 ng/mL (reference range, <11.4 ng/mL). A positron emission tomography–computed tomography scan was negative, as well as a c-KIT mutation analysis. A review of the skin biopsy from 9 years prior demonstrated slight acanthosis with dermal proliferation of mononuclear cells (Figure 2A), some of which had abundant cytoplasm and oval-shaped nuclei. There were few eosinophils and marked dermal telangiectasias. Giemsa stain revealed increased numbers of MCs in the upper dermis (Figure 2B). A bone marrow biopsy performed 9 years later showed multifocal lesions composed of MCs with associated lymphoid aggregates without notable myelodyspoiesis (or myeloproliferative neoplasm). These features were all consistent with WHO criteria for ISM. Based on the most current clinical, laboratory, and histopathologic findings, the patient was diagnosed with category IB ISM.

The patient’s symptoms had remained stable for 9 years with a regimen of triamcinolone cream 0.1% twice daily, doxepin cream 5% daily as needed, and oral fexofenadine 180 mg once daily. The patient continues to use topical steroids and oral antihistamines. Due to inadequate symptom control, breakthrough pruritus, and the development of new skin lesions on the head and neck, she was started on NB-UVB treatment 2 months after presentation. The patient’s symptoms and the extent of cutaneous maculopapular lesions improved after 20 light treatments (Figure 1B), with even more dramatic results after 40 cycles of therapy (Figure 1C). Overall, the lower legs have proved most recalcitrant to this treatment modality. She is currently continuing to receive NB-UVB treatment twice weekly.

Comment

Systemic mastocytosis is a heterogeneous disorder characterized by the proliferation and accumulation of atypical MCs in tissues, principally in the bone marrow and skin, though involvement of the gastrointestinal tract, liver, spleen, and lymphatic system also have been reported.^1,2,6 The WHO classification of mastocytosis divides this condition into 7 subtypes.⁴ Indolent systemic mastocytosis is the most common variant.^2,6 The etiology of ISM is not fully understood, but there is evidence suggesting that an activating mutation of KIT proto-oncogene receptor tyrosine kinase, KIT (usually D816V), present in the MCs of nearly 80% of patients with ISM may be involved.^1,3-5,7 Patients occasionally present with predominantly cutaneous findings but typically seek medical attention due to the recurrent systemic symptoms of the disease (eg, pruritus, flushing, syncope, palpitations, headache, dyspepsia, vomiting, diarrhea), which are related to the release of MC mediators.^1,2

The management of ISM is complex and based primarily on symptom reduction without alteration of disease course.^1,2,5,7 Patients should avoid symptom triggers such as heat, humidity, emotional and physical stress, alcohol, and certain medications (ie, aspirin, opioids, radiocontrast agents).⁷ Patients are initially treated with histamine H1- and H2-receptor antagonists to alleviate MC mediator release symptoms.^1,2,8 Although H1 blockers are most effective in mitigating cutaneous symptoms and limiting pruritus, H2 blockers are used to control gastric hypersecretion and dyspepsia.² Proton pump inhibitors are useful in patients with peptic ulcer disease who are unresponsive to H2-receptor antagonist therapy.^2,7 Cromolyn sodium and ketotifen fumarate are MC stabilizers that help prevent degranulation, which is helpful in relieving most major ISM symptoms. Leukotriene antagonists, such as zafirlukast, montelukast sodium, or zileuton, also may be employed to target the proinflammatory and pruritogenic leukotrienes, also products of the MC protein.^2,7 Imatinib mesylate and masitinib mesylate, both tyrosine kinase inhibitors, have been shown to improve symptoms and reduce MC mediator levels in ISM; however, most patients harbor the resistant KIT D816V mutation, which limits the utility of this medication.Patients with sensitive KIT mutations or those who have the wild-type KIT D816 mutation may be more appropriate candidates for imatinib or masitinib therapy, which can ameliorate symptoms of flushing, pruritus, and depression.^7-10 Treatment with omalizumab, a humanized murine anti-IgE monoclonal antibody, can be effective in treating recurrent, treatment-refractory anaphylaxis in ISM patients.^5,7

Symptoms unresponsive to these therapies can be effectively treated with a short course of oral corticosteroids,^6,7 while MC cytoreductive therapies such as interferon alfa or 2-chlorodeoxyadenosine (cladribine/2-CdA) are reserved for refractory cases.^2,7 Alternative therapies such as NB-UVB² or psoralen plus UVA phototherapy¹¹ also have demonstrated success in treating ISM symptoms. In the past, NB-UVB has shown efficacy in controlling pruriginous conditions ranging from chronic urticaria^12,13 to atopic dermatitis¹⁴ to psoriasis.¹⁵ This evidence has spurred studies to evaluate if NB-UVB has a role in the management of uncontrolled cases of cutaneous and ISM.^2,13,16,17 To date, the evidence has been promising. The majority of patients treated with this regimen report subjective reduction in pruritus in addition to clinical cutaneous disease burden.^2,11 Also, laboratory analysis demonstrates decreased levels of tryptase in patients utilizing NB-UVB phototherapy.² Thus far, the use of NB-UVB phototherapy in the treatment of pruriginous disorders such as ISM has not been associated with any severe side effects such as increased rates of anaphylaxis, though some research has suggested that this therapy may lower the threshold for patients to develop symptomatic dermographism.¹² Overall, patients treated with NB-UVB phototherapy report improved quality of life related to more effective symptom control.¹⁶

Although ISM is currently considered an incurable chronic condition,⁶ this case illustrates that symptomatic management is possible, even in cases of long-standing, severe disease. Patients should still be encouraged to avoid triggering factors and be vigilant in preventing potential anaphylaxis. However, NB-UVB phototherapy provides a supplemental or alternative treatment choice when other therapies have failed. We hope that the success of NB-UVB demonstrated in this case provides further evidence that this light-based therapy is a valuable treatment option in mastocytosis patients with unremitting or poorly controlled symptoms.

Systemic mastocytosis is a heterogeneous disorder of stem cell origin defined by abnormal hyperplasia and accumulation of mast cells (MCs) in one or more tissues.^1,2 The most commonly affected tissues are the bone marrow, gastrointestinal tract, and skin. Based on a number of major and minor criteria defined by the World Health Organization (WHO), the mastocytoses are subdivided into 7 variants that range from isolated cutaneous involvement to widespread systemic disease.^1-4 The most frequently diagnosed subtype is indolent systemic mastocytosis (ISM), a chronic disorder characterized by diffuse cutaneous macules and papules as well as bone marrow involvement in the form of multifocal dense infiltrates of MCs that frequently are phenotypically positive for c-KIT and tryptase. Serum tryptase levels are nearly invariably elevated in patients with this condition.^1,2

Symptoms of ISM are determined by the intermittent release of histamine and leukotrienes from hyperproliferating MCs as well as IL-6 and eosinophil chemotactic factors. As the burden of MC secretory products increases, patients experience worsening pruritus, flushing, palpitations, vomiting, and anaphylaxis in severe instances.^1,2,5 The mainstay of treatment of this condition involves symptom control through the inhibition of MC mediators.¹ The majority of patients respond well to antihistamines, antileukotriene agents, and oral corticosteroids during severe episodes of MC degranulation.^1,2,5

Unfortunately, some patients are unable to achieve adequate symptom control through the use of mediator-targeting treatments alone. In these cases, physicians often are faced with the following treatment dilemma: Either attempt to use therapies such as interferon alfa, which is cytoreductive to MCs, or 2-chlorodeoxyadenosine to reduce the overall MC burden, or turn to newer nonimmunosuppressive second-line options. We present the case of a patient with chronic ISM with progressive cutaneous lesions and poorly controlled pruritus that was previously managed with topical corticosteroids and antihistamines who responded favorably to treatment with narrowband UVB (NB-UVB) phototherapy.

Case Report

A 57-year-old woman presented with a 10-year history of widespread red-brown macules and papules on the trunk and upper and lower extremities. The lesions were intermittently pruritic, a symptom that was exacerbated on sun and heat exposure. A skin biopsy performed by an outside dermatologist 9 years prior confirmed the presence of mastocytosis. The patient was originally treated with triamcinolone cream and oral antihistamines, which controlled her symptoms successfully for nearly a decade.

At the current presentation, the patient reported increasingly severe pruritus and lesional spread to the neck and face of 15 months’ duration. She denied any symptoms of flushing, diarrhea, syncopal episodes, or lightheadedness. Physical examination revealed a well-appearing middle-aged woman with multiple 3- to 8-mm, red-brown, blanchable macules and papules with areas coalescing into plaques that primarily involved the legs (Figure 1A); arms; back; and to a lesser extent the abdomen, neck, and face. There was no palpable lymphadenopathy.

Laboratory results revealed a complete blood cell count and basic metabolic profile within reference range; however, the serum tryptase level was elevated at 65 ng/mL (reference range, <11.4 ng/mL). A positron emission tomography–computed tomography scan was negative, as well as a c-KIT mutation analysis. A review of the skin biopsy from 9 years prior demonstrated slight acanthosis with dermal proliferation of mononuclear cells (Figure 2A), some of which had abundant cytoplasm and oval-shaped nuclei. There were few eosinophils and marked dermal telangiectasias. Giemsa stain revealed increased numbers of MCs in the upper dermis (Figure 2B). A bone marrow biopsy performed 9 years later showed multifocal lesions composed of MCs with associated lymphoid aggregates without notable myelodyspoiesis (or myeloproliferative neoplasm). These features were all consistent with WHO criteria for ISM. Based on the most current clinical, laboratory, and histopathologic findings, the patient was diagnosed with category IB ISM.

The patient’s symptoms had remained stable for 9 years with a regimen of triamcinolone cream 0.1% twice daily, doxepin cream 5% daily as needed, and oral fexofenadine 180 mg once daily. The patient continues to use topical steroids and oral antihistamines. Due to inadequate symptom control, breakthrough pruritus, and the development of new skin lesions on the head and neck, she was started on NB-UVB treatment 2 months after presentation. The patient’s symptoms and the extent of cutaneous maculopapular lesions improved after 20 light treatments (Figure 1B), with even more dramatic results after 40 cycles of therapy (Figure 1C). Overall, the lower legs have proved most recalcitrant to this treatment modality. She is currently continuing to receive NB-UVB treatment twice weekly.

Comment

Systemic mastocytosis is a heterogeneous disorder characterized by the proliferation and accumulation of atypical MCs in tissues, principally in the bone marrow and skin, though involvement of the gastrointestinal tract, liver, spleen, and lymphatic system also have been reported.^1,2,6 The WHO classification of mastocytosis divides this condition into 7 subtypes.⁴ Indolent systemic mastocytosis is the most common variant.^2,6 The etiology of ISM is not fully understood, but there is evidence suggesting that an activating mutation of KIT proto-oncogene receptor tyrosine kinase, KIT (usually D816V), present in the MCs of nearly 80% of patients with ISM may be involved.^1,3-5,7 Patients occasionally present with predominantly cutaneous findings but typically seek medical attention due to the recurrent systemic symptoms of the disease (eg, pruritus, flushing, syncope, palpitations, headache, dyspepsia, vomiting, diarrhea), which are related to the release of MC mediators.^1,2

The management of ISM is complex and based primarily on symptom reduction without alteration of disease course.^1,2,5,7 Patients should avoid symptom triggers such as heat, humidity, emotional and physical stress, alcohol, and certain medications (ie, aspirin, opioids, radiocontrast agents).⁷ Patients are initially treated with histamine H1- and H2-receptor antagonists to alleviate MC mediator release symptoms.^1,2,8 Although H1 blockers are most effective in mitigating cutaneous symptoms and limiting pruritus, H2 blockers are used to control gastric hypersecretion and dyspepsia.² Proton pump inhibitors are useful in patients with peptic ulcer disease who are unresponsive to H2-receptor antagonist therapy.^2,7 Cromolyn sodium and ketotifen fumarate are MC stabilizers that help prevent degranulation, which is helpful in relieving most major ISM symptoms. Leukotriene antagonists, such as zafirlukast, montelukast sodium, or zileuton, also may be employed to target the proinflammatory and pruritogenic leukotrienes, also products of the MC protein.^2,7 Imatinib mesylate and masitinib mesylate, both tyrosine kinase inhibitors, have been shown to improve symptoms and reduce MC mediator levels in ISM; however, most patients harbor the resistant KIT D816V mutation, which limits the utility of this medication.Patients with sensitive KIT mutations or those who have the wild-type KIT D816 mutation may be more appropriate candidates for imatinib or masitinib therapy, which can ameliorate symptoms of flushing, pruritus, and depression.^7-10 Treatment with omalizumab, a humanized murine anti-IgE monoclonal antibody, can be effective in treating recurrent, treatment-refractory anaphylaxis in ISM patients.^5,7

Symptoms unresponsive to these therapies can be effectively treated with a short course of oral corticosteroids,^6,7 while MC cytoreductive therapies such as interferon alfa or 2-chlorodeoxyadenosine (cladribine/2-CdA) are reserved for refractory cases.^2,7 Alternative therapies such as NB-UVB² or psoralen plus UVA phototherapy¹¹ also have demonstrated success in treating ISM symptoms. In the past, NB-UVB has shown efficacy in controlling pruriginous conditions ranging from chronic urticaria^12,13 to atopic dermatitis¹⁴ to psoriasis.¹⁵ This evidence has spurred studies to evaluate if NB-UVB has a role in the management of uncontrolled cases of cutaneous and ISM.^2,13,16,17 To date, the evidence has been promising. The majority of patients treated with this regimen report subjective reduction in pruritus in addition to clinical cutaneous disease burden.^2,11 Also, laboratory analysis demonstrates decreased levels of tryptase in patients utilizing NB-UVB phototherapy.² Thus far, the use of NB-UVB phototherapy in the treatment of pruriginous disorders such as ISM has not been associated with any severe side effects such as increased rates of anaphylaxis, though some research has suggested that this therapy may lower the threshold for patients to develop symptomatic dermographism.¹² Overall, patients treated with NB-UVB phototherapy report improved quality of life related to more effective symptom control.¹⁶

Although ISM is currently considered an incurable chronic condition,⁶ this case illustrates that symptomatic management is possible, even in cases of long-standing, severe disease. Patients should still be encouraged to avoid triggering factors and be vigilant in preventing potential anaphylaxis. However, NB-UVB phototherapy provides a supplemental or alternative treatment choice when other therapies have failed. We hope that the success of NB-UVB demonstrated in this case provides further evidence that this light-based therapy is a valuable treatment option in mastocytosis patients with unremitting or poorly controlled symptoms.