Preoperative C-reactive protein-augmented CONUT score as a better prognostic indicator than CONUT alone in non-small cell lung cancer across age groups.

Background: Preoperative nutritional status correlates with outcomes in malignancies. We previously identified the Controlling Nutritional Status (CONUT) score as a sensitive prognostic indicator in elderly non-small cell lung cancer (NSCLC) patients and proposed the C-reactive protein (CRP)-augmented combined CRP and CONUT (C-CONUT) score. The aim of this study was to evaluate whether the C-CONUT score is a more effective prognostic tool than the CONUT score in younger NSCLC patients across different age groups. Methods: In a retrospective single-center cohort from January 2012 to December 2022 (n=738), we evaluated CONUT and C-CONUT scores in NSCLC patients across three age cohorts (≤79, ≤75, and ≤65 years). Patients receiving neoadjuvant therapy, with stage 0/IIIB disease, or missing data were excluded. Receiver operating characteristic (ROC) curves determined optimal cutoff values; Kaplan-Meier and multivariable Cox regression assessed prognostic significance. Results: Median follow-up was 56 months. Optimal cutoffs: CONUT ≥2; C-CONUT ≥3. C-CONUT achieved the highest area under the curve (AUC) [0.654; 95% confidence interval (CI): 0.653-0.781; P<0.001], outperforming CONUT alone. While elevated CONUT was prognostic only in patients ≤79 years, C-CONUT remained significantly associated with overall survival (OS) in all age strata, including ≤75 and ≤65 years. In multivariate models, C-CONUT was an independent predictor in younger cohorts even when CONUT was not. Conclusions: The C-CONUT score may be a more promising prognostic indicator than CONUT alone in NSCLC patients aged ≤75 years; however, this exploratory study requires prospective validation to confirm these findings. As it derives from routine laboratory parameters, C-CONUT is a practical, non-invasive tool for preoperative risk stratification. Prospective validation is warranted.