Long-term efficacy of BRAFi/MEKi rechallenge in metastatic melanoma: Report of 9 years of clinical practice.

Abstract

e21550 Background: First line BRAFi/MEKi therapy in metastatic melanoma eventually result in drug resistance and disease progression. Because drug resistance develops at least partially by epigenetic mechanisms, it may potentially be reversed after BRAFi/MEKi discontinuation. Therefore we aim to explore the clinical efficacy of BRAFi/MEKi rechallenge in 3 line treatment. Moreover the reports on the efficacy of BRAFi/MEKi after immunotherapy were contradictory, so we enrolled patients treated sequentially to explore this clinical scenario. Methods: In country-wide multicenter retrospective analysis 86 patients with metastatic BRAF-mutated melanoma were enrolled since 1/Jan/2014. Patients were treated with 1st line BRAFi/MEKi, 2nd line immunotherapy (anti-PD-1 or anti-CTLA-4) and were rechallenged with BRAFi/MEKi. Survival analyses were performed using the Kaplan-Meier method, log-rank and chi-square tests were used for comparison between groups. Data cut-off was 31/Dec/2022. Results: Median age at BRAFi/MEKi rechallenge was 50 (range: 20-81 y/o). Median overall survival (OS) from the start of the first BRAFi/MEKi therapy and from rechallenge BRAFi/MEKi treatment was 34 and 9 months, respectively; whereas median progression-free survival (PFS) was 10.5 and 4.4 months respectively. At the time of analysis 88% progressed on third line therapy and 78% patients died. Six-month, one-year, and two-year OS rates were: 99%, 93% and 70% on first line treatment; and 65%, 40% and 2% on BRAFi/MEKi rechallenge. Objective response rate and disease control rate on first line BRAFi/MEKi and rechallenge were 57% and 28%; and 91% and 64%, respectively. A lower toxicity rate was noted with BRAFi/MEKi rechallenge. The most common treatment sequence was dabrafenib/trametinib – immunotherapy – encorafenib/binimetinib. Conclusions: Rechallenge with BRAFi/MEKi after second line immunotherapy results in a clinically significant benefit in majority of eligible patients. Third line treatment should be considered for fit patients. [Table: see text]