Roles of adjuvant and salvage radiotherapy for desmoplastic melanoma

Current guidelines are unclear as to the precise role of radiotherapy (RT) in patients with desmoplastic melanoma (DM). The purpose of this study was to evaluate our institutional outcomes in patients with DM, and to explore the roles of both adjuvant and salvage RT in these patients. We identified 100 patients with a histopathologic diagnosis of DM who received treatment at our institution from 2000 to 2014. Local control, distant metastasis-free survival, and overall survival (OS) were evaluated in the 95 patients managed surgically with or without adjuvant and/or salvage RT. The overall rate of local recurrence (LR) was 10%. There was no LR in either adjuvant or salvage RT cohort. Adjuvant RT did not significantly improve LR-free survival at 5 years (100 vs. 81%, P=0.59), despite the RT patients having worse pathological features. Four of seven (57%) salvage patients developed distant metastases, despite 100% local control. Adjuvant RT did not significantly impact 5-year overall survival (86 vs. 82%, P=0.43). RT shows a trend towards improved local control in both the adjuvant and salvage settings for patients with DM, and likely overcomes adverse risk factors after surgery in appropriately selected patients. Future prospective studies are needed to better address the optimal management for these patients.