Sarcopenia, or the loss of skeletal muscle mass, has been increasingly recognized as a significant factor impacting outcomes in various cancers. Specifically, it has been reported as a poor prognostic indicator for patient survival. However, the relationship between skeletal muscle mass and prognosis in metastatic renal cell carcinoma (RCC) treated with immune checkpoint inhibitors (ICIs) remains complex, partly due to the heterogeneity of the patient population. To address this, we aimed to investigate the prognostic value of the psoas muscle volume index (PMVI) measured prior to first-line ICI therapy and its association with survival outcomes in intermediate- and poor-risk metastatic RCC patients classified by the IMDC criteria.

We conducted a retrospective review of data from 69 metastatic RCC patients with IMDC intermediate- and poor-risk who received first-line ICI treatment at our hospital from March 2019 to March 2024. PMVI was assessed using pre-treatment computed tomography scans, quantified with Synapse Vincent software, and calculated as the psoas major muscle volume divided by height squared (cm3/m2). Based on PMVI values, patients with PMVI <100 were categorized as Group A and those with PMVI ≥100 as Group B. We performed survival analyses to evaluate progression-free survival (PFS) and overall survival (OS), identifying significant factors that might serve as predictors of patient prognosis.

The median follow-up period for all patients was 379 days. Across the cohort, the median PMVI was 106.8 cm3/m2. Group A comprised 27 patients (39.1%), while Group B included 42 patients (60.9%). In Group A, the median PFS was 12.3 months, compared to 16.0 months in Group B (p = 0.0414). OS was also notably different, with Group A experiencing a median OS of 14.6 months, while Group B had a significantly extended OS of 49.1 months (p = 0.034). Multivariate analysis indicated that PMVI <100 was the only independent prognostic factor for both PFS (P=0.014, HR=3.91) and OS (P=0.002, HR=5.59), emphasizing its potential role in prognostic evaluation.

Our findings suggest that low PMVI may be associated with poorer survival outcomes in patients with metastatic RCC undergoing ICI therapy, as evidenced by shorter PFS and OS in patients with PMVI <100. As such, PMVI has potential utility as an objective and accessible prognostic biomarker that could aid in the risk stratification of metastatic RCC patients in clinical practice. Further studies are warranted to validate these findings and explore their clinical implications in broader patient populations.