Association between C-reactive protein-to-albumin ratio and the risk of overall survival in advanced non-small cell lung cancer patients with anlotinib treatment: a retrospective cohort study

The C-reactive protein-to-albumin ratio (CAR) reflects systemic inflammation and malnutrition, but its association with survival in anlotinib-treated advanced non-small cell lung cancer (NSCLC) remains unexplored. We retrospectively analyzed 417 patients with stage IIIB-IV NSCLC treated with anlotinib at Zhongshan Hospital, Fudan University and Zhongshan Hospital (Xiamen), Fudan University. Baseline CAR was calculated as serum C-reactive protein (mg/L) divided by albumin (g/L). Overall survival (OS) was defined as the time from treatment initiation to death or last follow-up. Cox proportional hazards models, restricted cubic spline (RCS) analysis, and two-piecewise linear regression model were applied to evaluate the association between CAR and OS. Subgroup analyses were further performed for robustness. Among 417 patients (mean age 62.2 ± 10.33 years), 216 deaths (51.8%) occurred during follow-up. The median CAR was 0.34 (0.08–1.09). In multivariable Cox models, elevated CAR was independently associated with worse OS (HR 1.10, 95% CI 1.01–1.21, p = 0.031). RCS analysis revealed a nonlinear association between CAR and OS (p for nonlinearity < 0.001). The inflection point was 2.12: below this threshold, higher CAR significantly increased mortality risk (HR 1.92, 95% CI 1.54–2.40, p < 0.0001), whereas above 2.12, CAR showed a non-significant trend toward lower risk (HR 0.82, 95% CI 0.68–1.00, p = 0.050). Subgroup analyses demonstrated consistent associations across most clinical strata. Baseline CAR is a strong and independent prognostic marker for OS in advanced NSCLC patients treated with anlotinib. Its simplicity and availability make it a valuable tool for clinical risk stratification and treatment planning.