Prognostic Role of the C-PLAN Index in Metastatic Melanoma: A Two-Center Retrospective Study

Background: The C-PLAN index is a composite prognostic tool incorporating clinical, inflammatory, nutritional, and biochemical parameters. Its prognostic role in metastatic melanoma remains insufficiently investigated. This study aimed to evaluate the association between the C-PLAN index and survival outcomes in patients with metastatic melanoma. Methods: This retrospective two-center study included 130 patients with metastatic melanoma treated at Erciyes University and Erzurum City Hospital between January 2012 and September 2023. The C-PLAN index was calculated using five parameters: Eastern Cooperative Oncology Group performance status, C-reactive protein, lactate dehydrogenase, serum albumin, and derived neutrophil-to-lymphocyte ratio (dNLR). Patients were classified into C-PLAN score groups of 0–1 and ≥2. Progression-free survival (PFS) and overall survival (OS) were evaluated using Kaplan–Meier analysis and Cox proportional hazards regression. Results: Among the 130 patients, 48 (36.9%) had a C-PLAN score of 0–1 and 82 (63.1%) had a score of ≥2. During follow-up, 76 patients experienced a PFS event, and 94 died. Median PFS was longer in the C-PLAN 0–1 group than in the ≥2 group (30.27 vs. 9.17 months; log-rank p < 0.001). Median OS was also longer in the C-PLAN 0–1 group (82.93 vs. 29.70 months; log-rank p < 0.001). In the multivariable Cox regression analysis for PFS, a C-PLAN score of ≥2 was associated with a higher hazard of progression or death (HR, 3.193; 95% CI, 1.774–5.746; p < 0.001). A higher number of metastatic sites, BMI category, mitotic activity, lymphatic invasion, and BRAF status were also independently associated with PFS. In the multivariable Cox regression analysis for OS, a C-PLAN score of ≥2 (HR, 3.227; 95% CI, 1.910–5.455; p < 0.001) and a higher number of metastatic sites (HR, 2.453; 95% CI, 1.538–3.912; p < 0.001) were independently associated with a higher hazard of death. Conclusions: In this retrospective two-center cohort, a C-PLAN score of ≥2 was associated with shorter PFS and OS. These findings should be interpreted as exploratory and support further investigation of C-PLAN as a prognostic index in melanoma. Validation in larger, contemporary, and independent cohorts is required before its clinical utility can be established.