Combination of Immunotherapy and Brain Radiotherapy in Metastatic Melanoma: A Retrospective Analysis

Background: Up to 40% of patients with metastatic melanoma (MM) develop brain metastases. Radiotherapy (RT) may potentiate the effects of immunotherapy (IO), even on distant sites (abscopal effect). Material and Methods: We retrospectively analyzed all our MM patients treated with IO within 6 months before/after brain RT between 2012 and 2016. Progression-free (PFS) and overall survival (OS) were estimated with the Kaplan-Meier method and compared with those of controls treated with IO during the same period. Results: Thirty-six cases and 25 controls were identified. Among cases, 23 patients received an anti-CTLA4 agent and 13 an anti-PD1 agent. Eighteen cases were treated with stereotactic RT and 18 with whole-brain RT. Median PFS from the beginning of RT was 4 months in first-line and 2 months in second-line treatment. A third of the cases progressed at first evaluation after RT. Median OS from the beginning of RT was 7 months in first-line and 4 months in second-line treatment. Median PFS and OS of each treatment line showed a trend towards inferiority compared with those of controls. Conclusion: Synergism between RT and IO was not observed in our case series. No cases of abscopal effect were seen, and most patients underwent early systemic progression after RT.