Durable local control with hypofractionated radiation therapy for unresectable or metastatic melanoma.

Background and purpose: As patients with advanced melanoma live longer in the context of systemic therapy advancements, better strategies for durable control of bulky tumors are needed. In this study, we evaluated if dose-escalated hypofractionated radiation therapy (HFRT) can provide durable local control and improve tumor-associated symptoms in patients with unresectable or bulky metastatic melanoma for whom stereotactic ablative radiotherapy (RT) approaches are not feasible due to tumor size or location. Materials and methods: We retrospectively reviewed 49 patients with unresectable or bulky metastatic melanoma who were treated to a total of 53 tumor targets with 12-17 fractions HFRT at our institution between 2015-2022. Clinical scenarios included: unresectable, locoregional only disease (26 %); oligometastatic disease (<3 total sites, 17 %); oligoprogressive disease (<3 sites progressing, 17 %); and aggressive palliation (>5 known sites of disease or with at least 3 sites progressing, 40 %). Results: Of the 53 HFRT targets, 91 % (n = 48) had radiographic evidence of response as defined by either stabilization (6 %, n = 3), decreased size (74 %, n = 39), or decreased FDG avidity (11 %, n = 6). Of the 43 symptomatic patients, 98 % (n = 42) had symptomatic improvement. One -year local control was 79 %, with 2-year progression-free and overall survival of 33 % and 39 % respectively. The most common acute toxicities were radiation dermatitis (16 %, n = 8) or a pain flare (14 %, n = 7). Late toxicities were uncommon and typically grade 1. Conclusion: HFRT provides favorable local control and symptomatic relief with limited toxicity in tumors not amenable to surgical resection or stereotactic ablative RT.