Radiation therapy is used infrequently for cutaneous melanoma, despite research suggesting benefit in certain clinical scenarios. This review presents data forming the highest level of evidence supporting the use of radiation therapy. Retrospective and prospective studies demonstrate radiation therapy for primary tumors is associated with high control rates. Two randomized trials have found improvements in regional control with adjuvant radiotherapy to regional lymphatics. Retrospective and prospective studies demonstrate radiation therapy is associated with palliative response and metastatic tumor control. Optimal care of melanoma patients involves radiation therapy; awareness of this is incumbent of clinicians caring for patients with this disease.
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Radiation therapy is infrequently used in the care of patients with cutaneous melanoma, despite research suggesting a benefit in certain clinical scenarios.
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Definitive radiation therapy may be a viable treatment option for lentigo maligna and lentigo maligna melanoma.
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Adjuvant radiation therapy to the site of a resected neurotropic melanoma may improve local control of the tumor.
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Adjuvant radiation therapy to the site of resected lymph node metastases from melanoma at high risk for recurrence may improve regional control of lymphatic metastases.
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Palliative radiation therapy is likely to yield a response in patients with distant metastases.
Introduction
In 2002, the Collaboration for Cancer Outcomes Research and Evaluation of Australia estimated that over the course of their disease approximately 23% of patients diagnosed with cutaneous melanoma (CM) would be appropriately treated with radiation therapy (RT) based on the best available evidence. Using population registry data, these investigators found that RT was part of the treatment of 13% of patients in New South Wales, Australia, and 1% to 6% of patients in the United States. Others have noted the infrequent and dwindling use of RT for CM over time. Awareness of the evidence supporting the use of RT for the treatment of CM is vital to delivering the optimal care of patients with this potentially lethal disease.
Several general aspects of RT for melanoma are not addressed in this review. The myth that melanoma is not responsive to RT has been adequately described and dispelled elsewhere. The curative and organ-preserving potential of RT for uveal melanoma has been demonstrated by the Collaborative Ocular Melanoma Study and is beyond the scope of this review. Likewise, the role of RT in the management of mucosal melanoma is beyond the scope of this article. Herein, data providing the highest levels of evidence supporting the use of RT for CM are presented and discussed, acknowledging a significant dearth of high-level evidence in many situations.
Radiation therapy for the primary tumor
Although the effective use of RT as definitive local therapy for primary CM has been described, the therapeutic modality of choice for resectable CM in the medically operable patient is surgery. At present, pathologic staging by surgery provides the most valuable prognostic information available for early-stage CM. However, there are situations in which surgery might preclude acceptable functional or cosmetic outcomes to some patients.
Definitive Radiation Therapy for Lentigo Maligna and Lentigo Maligna Melanoma
Most frequently, RT for the primary tumor is considered for lentigo maligna (LM) and lentigo maligna melanoma (LMM). Because patients with LM and LMM are often elderly and present with large, superficial lesions on the face, alternatives to surgery are often considered to optimize cosmetic and functional outcome. Table 1 summarizes the outcome of RT for LM and LMM from the largest updated retrospective series from around the world. Although follow-up has been limited, the pooled results demonstrate that the efficacy of RT compares favorably with other treatment modalities. Of note, relatively high rates of local recurrence have been noted in several series from North America, and may be related to RT technique. Although toxicity generally depends on the technique used, the outcome of skin RT is generally acceptable to elderly patients, in whom LM and LMM are most common.
| Origin of Study Ref. | Disease | Patients | Local Recurrence | Lymphatic Recurrence | Distant Recurrence | Follow-Up | |||
|---|---|---|---|---|---|---|---|---|---|
| n | n | % | n | % | n | % | |||
| Netherlands | LM | 21 | 1 | 5 | 0 | 0 | 0 | 0 | Median 3 y |
| Switzerland | LM | 93 | 5 | 5 | 0 | 0 | 0 | 0 | Not reported (101 patients followed for at least 2 y) |
| LMM | 54 | 0 | 0 | 2 | 4 | 0 | 0 | ||
| Germany | LM | 42 | 0 | 0 | 0 | 0 | 0 | 0 | Median 1.3 y |
| LMM | 22 | 2 | 9 | 0 | 0 | 1 | 5 | ||
| USA | LM | 15 | 4 | 27 | 1 | 7 | 3 | 20 | Median 2.7 y |
| LMM | 1 | 0 | 0 | 0 | 0 | 1 | 100 | ||
| Canada | LM | 36 | 4 | 11 | 0 | 0 | 0 | 0 | Median 6 y |
| Canada | LM | 31 | 9 | 29 | Median 3.9 y | ||||
| Australia | LM | 7 | 0 | 0 | 0 | 0 | 0 | 0 | Median 1.3 y |
| Pooled estimates | LM | 245 | 23 | 9 | 1 | 0 | 3 | 1 | |
| LMM | 77 | 2 | 3 | 2 | 3 | 2 | 3 | ||
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