Background: Oligoprogression is a limited progression after a prior response to treatment. Oligoprogression remains a major clinical challenge in patients with metastatic melanoma (MM). Local therapy for progressing metastases may enable the continuation of effective systemic therapy. Methods: We identified 77 patients treated with radiotherapy combined with hyperthermia for oligoprogressive MM in a melanoma tertiary center between 2019 and 2022. Patients without any follow-up imaging after irradiation were excluded. We assessed local control (LC), and overall survival (OS). We estimated the correlation between BRAF status, size of the irradiated lesion, radiation dose, and LC. Survival analyses were performed using the Kaplan-Meier estimator, and Log-rank tests and were used for comparison between groups. The data cut-off was 31/Aug/2022. Results: The majority of patients (83%) had one oligoprogressive lesion. At the time of analysis, 59.5% of patients had stable disease, complete or partial response, and 40.5% of patients had progression, in the total response according to RECIST (Table). Most patients (78%) were irradiated during immunotherapy whereas 12% received concomitant BRAF and MEK inhibitors (Table). There were no severe toxicities of radiotherapy nor hyperthermia. The median follow-up was 18 (95%CI: 16-24) months(m). The 12 and 24m LC rates were: 83% (95%CI: 74-94) and 54% (95%CI: 40-73), respectively. The achieved LC rate was 88.3%. The 12 and 24m OS rates were: 87% and 72%, respectively. At the time of analysis, the median of OS and LC were not reached. BRAF status, size of the lesion, or radiation dose were not associated with LC. Conclusions: Preliminary data showed that patients with MM may benefit from radiotherapy combined with hyperthermia for oligoprogressive lesions during systemic treatment. This combination enables good local control of progressive metastases with minimal toxicity. This topic requires further investigation in prospective studies.

* - at the time of analysis. RT - radiation therapy, HT - hyperthermia, IT - immunotherapy, BRAFi/MEKi - BRAF and MEK inhibitors, CHT - chemotherapy, CR - complete response, PR - partial response, SD - stable disease, PD - progression disease.