Impact of radiotherapy administered simultaneously with systemic treatment in patients with melanoma brain metastases within MelBase, a French multicentric prospective cohort

Abstract : Background: Melanoma brain metastases (MBMs) are historically associated with poor prognosis. Radiation therapy is conventionally associated with a high local control rate. Development of targeted therapy and immunotherapy has improved overall survival (OS) and intracranial response rate, but about 50% of patients failed to respond to these novel therapies. The objective of this study was to assess the impact of combined radiotherapy (cRT) on overall survival in a large multicenter real-life prospective cohort of patients with MBM treated with immunotherapy or targeted therapy.Patients and methods: Clinical data from 262 patients with MBM were collected via MelBase, a French multicentric biobank prospectively enrolling unresectable stage III or IV melanoma. Two groups were defined: patients receiving cRT (cRT group) or not receiving cRT (no-cRT group). Primary end-point was OS. Propensity score weighting was used to correct for indication bias.Results: Among the 262 patients, 93 (35%) received cRT (cRT group). The patients were treated with immunotherapy in 69% and 60% and with targeted therapy in 31% and 40% of the cRT and no-cRT groups, respectively. With a median follow-up of 6.9 months, median OS was 16.8 months and 6.9 months in the cRT and no-cRT groups, respectively. After propensity score weighting, cRT was associated with longer OS (hazard ratio = 0.6, 95% confidence interval: 0.4-0.8; p=0.007). Median OS after ponderation was 15.3 months and 6.2 months in the cRT and no-cRT groups, respectively.Conclusion: This study shows that cRT may be associated with a significant decrease of 40% in the risk of death in patients with MBM treated with systemic therapy.