Relationship of Muscle Mass Based on Psoas Muscle Index and Skeletal Muscle Index with Recurrence and Mortality Risk in Localized Renal Cell Carcinoma: A Comprehensive Retrospective Analysis

Objective: We aimed to determine the relationship between the Psoas Muscle Index (PMI) and Skeletal Muscle Index (SMI) and the risk of recurrence and mortality in patients with localized Renal Cell Carcinoma (RCC). Material and Methods: SMI and PMI values were obtained from non-contrast computed tomography (NCCT) measurements on slices at the L3 level, normalized by height. Available survival data, including overall survival (OS) and recurrence-free survival (RFS), were collected at postoperative follow-up. Disease recurrence was defined as radiological evidence of disease on computed tomography (CT), magnetic resonance imaging, or bone scan. Results: In the ROC analysis, the optimal cut-off value for PMI was ≤ 5.1 cm²/m² and ≤ 3.1 cm²/m² in male and female patients, while the cut-off value for SMI was ≤ 44 cm²/m² and ≤ 30 cm²/m² in male and female patients. In multivariate analyses, female gender, recurrence, clinical T stage ≥ T3b, pathological T stage ≥T3b, and sarcopenia according to PMI and SMI were independent predictors of worse OS and RFS (p < 0.001). In Kaplan-Meier analysis, OS in patients with and without sarcopenia was 74 vs 85 months (p < 0.001), respectively. RFS were shorter in patients with sarcopenia (PMI: 76 vs 84, SMI: 74 vs 85 months, both p < 0.001) Conclusion: In patients with localized RCC, sarcopenia was associated with earlier recurrence, shorter OS, and RFS. Patients with sarcopenia had a worse prognosis in preoperative staging.