Impact of combined skeletal muscle index, subcutaneous fat index, and visceral fat index on prognosis in non-metastatic non-small cell lung cancer

The combined prognostic role of skeletal muscle index (SMI), subcutaneous fat index (SFI), and visceral fat index (VFI) in non-metastatic non-small cell lung cancer (NSCLC) remains unclear. Consecutive non-metastatic NSCLC patients who underwent radical pulmonary resection at Yunnan Cancer Hospital from January 2013 to December 2018 were analyzed. Preoperative CT-derived SMI, SFI, and VFI at the third lumbar vertebra level (L3) were stratified into sex-specific high and low groups. A composite index was created based on the count of low-value measures among the three indices. Cox regression evaluated associations with overall survival (OS) and relapse-free survival (RFS). A total of 1661 patients (mean age 58.9 ± 9.5 years; 911 men [54.8%] and 750 women [45.2%]) were enrolled, with a median follow-up of 73.97 months (95% CI: 72.80–75.10). Low SMI (HR = 1.49, 95% CI: 1.16–1.92, p = 0.002), low SFI (HR = 1.54, 95% CI: 1.22–1.94, p < 0.001), and low VFI (HR = 1.69, 95% CI: 1.32–2.17, p < 0.001) were associated with poorer OS. The composite index demonstrated poorer OS with an increasing number of low indices (SMI, SFI, and VFI) (p for trend < 0.001): one-low (HR = 1.50, 95% CI: 1.16–1.94, p = 0.002), two-low (HR = 1.71, 95% CI: 1.29–2.28, p < 0.001), and all-low (HR = 2.99, 95% CI: 1.89–4.71, p < 0.001). Similar trend occurred for RFS (all p < 0.05). Preoperative SMI, SFI, and VFI were independently associated with prognosis in patients with NSCLC, and a composite index integrating these measures may provide valuable complementary information for risk stratification.