Prognostic value of different metabolic response criteria in patients with advanced melanoma treated with immunotherapy: a comparative analysis of PECRIT, PERCIMT, and EORTC criteria.

BACKGROUND: The optimal [18 F]FDG-PET/CT criteria for assessing metabolic response to immunotherapy in melanoma remain debated. This study aimed to compare the prognostic performance of PECRIT, PERCIMT, and EORTC criteria in a cohort of advanced melanoma patients. METHODS: We retrospectively evaluated patients with advanced melanoma undergoing immune checkpoint inhibitors (ICIs) therapy who underwent baseline and interim [18 F]FDG-PET/CT scans. A per-patient metabolic response was categorized as Complete (CMR), Partial (PMR), Stable (SMD), or Progressive Metabolic Disease (PMD) using PECRIT, PERCIMT, and EORTC criteria. Baseline tumor burden was assessed by lesion count and volumetric parameters (MTV, TLG) were explored. Response agreement between criteria was evaluated, and survival analysis (Overall Survival, OS, and Progression-Free Survival, PFS) was performed using Kaplan-Meier and Log-rank tests. Patients were further dichotomized into Disease Control Group (DCG: CMR + PMR+SMD) versus No-DCG (PMD), and Objective Response Group (ORG: CMR + PMR) versus Non-ORG (SMD + PMD). RESULTS: A total of 46 patients were included. At a median follow-up of 29.1 months, 30/46 patients (65%) progressed and 22/46 (48%) died, with a median OS of 24.6 months (IQR 13.9-41.4) and a median PFS of 10.7 months (IQR 5.3-24.7) for the entire cohort. Specifically, discordance between criteria occurred in 16/46 (35%) cases, predominantly involving PECRIT/EORTC PMD versus PERCIMT SMD (8 cases, 50% of the discordant cases). Prognostic analysis revealed significant differences in PFS and OS between response groups across all three evaluated criteria. Patients in the DCG had significantly longer PFS across all criteria (all p ≤ 0.012), and patients in the ORG had s significantly longer OS for PECRIT (p = 0.039) and EORTC (p = 0.003). CONCLUSION: All three criteria provide valuable prognostic insights for survival in immunotherapy-treated melanoma. However, notable discordance exists in response classification, particularly regarding the definition of progressive disease. The dichotomized approach (DCG/ORG) appears to represent a promising, clinically relevant tool to consolidate metabolic response assessment, facilitating a more consistent prediction of patient outcomes in the clinical setting.