Background Immune checkpoint inhibitor therapy (ICI) with nivolumab+ipilimumab is a first-line (1L) standard for metastatic clear cell renal cell carcinoma (ccRCC), yet outcomes remain heterogeneous. Increasing evidence suggests that host factors influence the tumor microenvironment and response to ICI. Although higher body mass index (BMI) has been associated with improved outcomes in several malignancies, BMI is an imprecise surrogate for underlying adipose and muscle compartments. We evaluated the association between body composition and outcomes with 1L nivolumab+ipilimumab in metastatic ccRCC. Methods We retrospectively analyzed patients with mccRCC treated with 1L nivolumab+ipilimumab at MD Anderson Cancer Center between June 2015 and February 2024. Body composition was measured using an artificial intelligence segmentation tool at the L3 vertebra from pretreatment CT scans obtained within 45 days prior to starting therapy. Endpoints included real-world progression-free survival (PFS) and overall survival (OS). Multivariable Cox regression models, guided by directed acyclic graphs, evaluated associations between continuous body composition measures and outcomes, incorporating non-linear cubic splines. An exploratory analysis used single-cell RNA sequencing from 12 treatment-naïve patients with metastatic ccRCC, stratified by median Skeletal Muscle Mass Index (SMMi) and Subcutaneous Adipose Tissue Index (SATi) values. Results Among 309 patients (80.3% male, median age 61.9 years; 61.8% intermediate-risk and 28.5% poor-risk), increasing SMMi and SATi were independently associated with shorter PFS (HR 1.50, 95% CI 1.05 to 2.15 per 3-unit increase; and HR 1.39, 95% CI 1.01 to 1.90 per 10-unit increase). The associations of BMI, visceral adiposity, and skeletal muscle density with PFS were inconclusive. OS associations for all body-composition measures were likewise indeterminate. In the single-cell cohort, low SMMi was associated with numerically higher T-cell fractions (p=0.064), fewer myeloid cell proportions (p=0.10), and higher IDO1 expression. Conclusions Greater subcutaneous adiposity and skeletal muscle mass were associated with shorter PFS among patients with metastatic ccRCC treated with 1L nivolumab+ipilimumab. These findings support the concept that host body composition influences the heterogeneous clinical benefit observed with ICI in metastatic ccRCC.
Grewal et al. (2026) studied this question.