Comparing survival outcomes in early stage desmoplastic melanoma with or without adjuvant radiation.

Desmoplastic melanoma (DM) due to its rare and locally aggressive nature, can be difficult to study and to treat effectively. Whether the optimal treatment approach for these tumors should include adjuvant radiation has been unclear in the literature. In this retrospective study of the National Cancer Database, 2390 patients with localized DM were included for analysis. 2082 were treated with wide local excision (WLE) and 308 were treated with wide local excision and adjuvant radiation therapy (WLE + RT). Overall survival (OS) in these groups was compared on crude and adjusted analyses utilizing Cox proportional hazards regression modeling. There was no difference in OS at 1, 3, and 5 years on initial analysis. Subsequent multivariate analysis and propensity score analysis showed a survival benefit in those treated with WLE + RT. Multivariate analysis demonstrated significantly decreased OS in cases of residual tumor following surgical excision. Adjuvant radiation was more likely to be performed for tumors on the head and neck, tumors with higher pathologic American Joint Committee on Cancer stage and T classifications, and tumors with positive surgical margins. This is the first study to demonstrate significantly improved OS in early-stage DM patients treated with WLE + RT compared to WLE alone.