Clinical outcomes in metastatic melanoma in Colombia: A retrospective cohort study from the REMMEC registry.

e21511 Background: Latin American melanoma data reflect distinct epidemiology and variable treatment access. REMMEC is a Colombian registry; survival estimates in stage IV disease remain limited. Methods: To characterize baseline features and first-line treatments and to evaluate overall survival (OS) and progression-free survival (PFS) in a Colombian metastatic melanoma cohort, we performed a retrospective cohort study of adults with stage IV melanoma in REMMEC (January 2011–June 2025) across multiple centers. Eligibility: histologically confirmed cutaneous or mucosal melanoma, distant metastases, age ≥18 years. Index date: stage IV diagnosis. OS was time from index to death; PFS was time from index to progression (RECIST v1.1 or investigator assessment) or death. Kaplan–Meier methods with log-rank tests compared groups. Cox models adjusted for age, sex, ECOG status, BRAF status, number of metastatic sites, and lactate dehydrogenase (reference: chemotherapy/other). Two-sided P<0.05 was significant. Multiple imputation for missing covariate data. Results: Mean age was 64 years (SD, 16); 55% male; 61% low-income. At initial presentation, 80% had stage IV disease. Primary site: cutaneous 70%, mucosal 30%; most common subtype was acral lentiginous melanoma (23%). BRAF testing was performed in 221 patients (61%), with mutations in 20% of those tested. First-line: immunotherapy monotherapy (n=161, 44%), dual-agent immunotherapy (n=54, 15%), BRAF/MEK inhibitors (n=22, 6%), chemotherapy/other (n=127, 35%). Adverse events 34% (any grade, CTCAE v5.0). Objective response 18.6% (complete 8.5%, partial 10.1%; RECIST v1.1). Median follow-up 29 months. Median OS 24 months (95% CI, 20–35); median PFS 21 months (95% CI, 18–26). Cutaneous melanoma: OS/PFS 32/25 months (95% CI, 24–58/20–32); mucosal melanoma: OS/PFS 19/17 months (95% CI, 13–NR/12–26; NR=not reached). By treatment—OS: immunotherapy 40 months (32–NR), BRAF/MEK 29 months (13–NR), chemotherapy/other 14 months (6–55); PFS: immunotherapy 32 months (25–40), BRAF/MEK 26 months (13–NR), chemotherapy/other 12 months (6–32). PFS events 167. Adjusted models showed improved OS and PFS with immunotherapy (OS HR 0.27 [95% CI, 0.15–0.49], P=0.001; PFS HR 0.35 [0.20–0.61], P=0.001). BRAF/MEK inhibitors were associated with longer OS (HR 0.43 [0.20–0.90], P=0.025) but not PFS (HR 1.36 [0.38–4.89], P=0.64; estimate imprecise due to small n). Metastatic burden ≥3 sites predicted shorter OS and PFS (OS HR 2.31 [1.30–4.11], P=0.004; PFS HR 2.21 [1.30–3.77], P=0.003). Conclusions: Immunotherapy was the predominant first-line approach and was associated with longer OS and PFS versus chemotherapy/other after adjustment. High stage IV and acral lentiginous prevalence support earlier detection strategies and expanded access to immune checkpoint inhibitors and targeted therapy.