Real-World Treatment Outcomes After Nivolumab Progression in BRAF-Negative Metastatic Melanoma: A Multicenter Cohort Study by the Turkish Oncology Group.

Background/Objectives: Despite improved survival with immune checkpoint inhibitors, the optimal treatment after anti-PD-1 progression in metastatic melanoma remains unclear. This study compared survival outcomes and treatment responses between chemotherapy (CT)- and immunotherapy (IO)-based therapies administered after nivolumab progression in patients with BRAF-negative metastatic melanoma. Methods: This multicenter retrospective study included patients with BRAF-negative metastatic melanoma who developed disease progression during nivolumab treatment. Post-progression systemic therapies were categorized as CT- or IO-based treatments. Treatment responses were assessed according to RECIST version 1.1 criteria. Progression-free survival (PFS) and overall survival (OS) were analyzed using the Kaplan-Meier method, and prognostic factors were evaluated using Cox regression analyses. Results: A total of 141 patients were included. Following nivolumab progression, 107 (75.9%) received CT and 34 (24.1%) received IO. Based on best response to nivolumab, the objective response rate (ORR; CR + PR) was 55.1% in the CT group and 44.1% in the IO group. After post-nivolumab treatment, ORRs were 29.9% and 32.4% in the CT and IO groups, respectively, whereas complete response rates were higher with IO (21.2% vs. 3.0%). Median PFS was 4.17 months in the CT group and 3.9 months in the IO group (p = 0.403). Median OS was 7.83 and 8.17 months, respectively (p = 0.416). Elevated LDH level was identified as an independent adverse prognostic factor. Conclusions: In this multicenter real-world cohort, no statistically significant differences in survival were observed between patients receiving CT or IO after nivolumab progression. Given the retrospective, non-randomized study design, these findings should not be interpreted as evidence of comparative treatment efficacy. The higher CR rate observed with IO should be interpreted cautiously due to potential selection bias. Prospective studies are warranted to define the optimal treatment strategy after anti-PD-1 failure.