Body Composition and Inflammatory-Metabolic Indices in Immunotherapy-Treated Metastatic Non-Small Cell Lung Cancer: The SARC-CTI Study

This retrospective, single-center observational cohort study evaluates inflammatory-metabolic, cachexia-related, and computed tomography (CT)-derived body-composition markers in patients with metastatic non-small cell lung cancer (mNSCLC) treated with immune checkpoint inhibitor (ICI)-based therapy. The study includes 155 consecutive adult patients who initiated ICI-based therapy at Ankara Etlik City Hospital between December 2022 and March 2025. Baseline assessments include the C-reactive protein-triglyceride glucose index (CTI), cachexia index (CXI), CT-derived skeletal muscle index (SMI), skeletal muscle attenuation, sarcopenia status, body weight, and clinical characteristics. The principal survival outcomes are progression-free survival (PFS) and overall survival (OS). Associations of baseline CTI and CXI with PFS and OS are evaluated using Cox proportional hazards regression models. The incremental prognostic performance of CTI and CXI beyond conventional clinical factors is further explored using discrimination, calibration, and decision-curve analyses. Early longitudinal changes in CT-derived body composition and body weight are evaluated in a landmark cohort of 140 patients with an eligible follow-up CT performed 8-12 weeks after ICI initiation. Associations of early skeletal muscle and body-weight changes with subsequent PFS and OS are assessed using landmark survival analyses. The survival data cutoff is June 11, 2026.