Clinical outcomes of multisite moderate to high dose radiotherapy for patients with metastatic melanoma.

Background and purpose: This study aimed to summarize the clinical outcomes of patients with metastatic melanoma who received high-dose radiation prior to or during systemic therapy at a single academic institution. Methods: We identified patients with metastatic melanoma who underwent high-dose radiation therapy (HDRT) for extracranial metastases prior to or during systemic therapy from 2010 to 2018. Treatment indications included oligometastases, oligoprogression, and local control. Using the Kaplan-Meier method, we plotted overall survival (OS), progression-free survival-1 (PFS1), and PFS2. Competing risk analysis determined the cumulative incidence of local failure (LF) and the time to start or change systemic therapy (SCST). Univariate and multivariable analyses were used to identify predictive factors. Results: We analyzed 34 patients with 79 lesions, with a median follow-up of 17.4 months. Sixty-eight percent of patients received systemic therapy after the first HDRT. The median OS was 22 months, with brain metastases before HDRT being a significant predictor in multivariable analysis. The median PFS1 for first-line HDRT was 4.1 months, and the median PFS2 was 3.9 months. Rates of LF were 10.3% at 12 months and 11.7% at 24 months. The incidence of SCST following HDRT was 59.8% at 12 months and 76.1% at 24 months, with radiation targeted at the lung associated with a lower incidence of SCST. Conclusion: HDRT for treating metastatic lesions in melanoma demonstrated excellent local control and may play a role in delaying SCST. Additional courses of HDRT may provide cumulative benefits.