Body Composition and Blood-Based Prognostic Markers in Immunotherapy-Treated Metastatic Non-Small Cell Lung Cancer

This study investigates the impact of sarcopenia and the CRP-TyG Index (CTI) on immunotherapy outcomes in patients with metastatic non-small cell lung cancer (NSCLC). Medical records of 115 adult patients treated with immune checkpoint inhibitors at Ankara Etlik City Hospital between November 2022 and December 2024 will be retrospectively analyzed. Sarcopenia will be determined from CT-based skeletal muscle index (SMI) measurements at the L3 vertebral level. SMI will be calculated as skeletal muscle area (cm²) divided by height squared (m²), with sex-specific cut-offs (≤52.4 cm²/m² for men, ≤38.5 cm²/m² for women). CTI will be calculated from CRP, triglycerides, and fasting glucose values. Primary outcome is objective response rate (ORR, RECIST 1.1). Secondary outcomes include 1-year progression-free survival (PFS), 1-year overall survival (OS), treatment duration, and adverse events (CTCAE v5.0).

Inclusion Criteria: * Age ≥18 years. * Histologically confirmed diagnosis of metastatic non-small cell lung cancer (mNSCLC). * Received at least one cycle of immune checkpoint inhibitor (PD-1 or PD-L1 inhibitor) as part of routine clinical care. * Availability of baseline CT imaging (within 4 weeks before treatment initiation) and follow-up CT imaging at approximately 3 months. * Availability of baseline laboratory data including C-reactive protein (CRP), triglycerides, and fasting glucose. * Adequate clinical records for evaluation of treatment response and survival outcomes. Exclusion Criteria: * Age \