The Prognostic Immune and Nutritional Index as a Predictor of Survival in Resected Non-Small Cell Lung Cancer

<i>Background and Objectives</i>: The prognostic immune and nutritional index (PINI), derived from serum albumin levels and absolute monocyte counts, has demonstrated prognostic value in gastrointestinal cancers. However, its role in non-small cell lung cancer (NSCLC) remains unclear. This study assessed the prognostic utility of the PINI for overall survival (OS) in patients with stage I-IIIA NSCLC undergoing curative-intent resection. <i>Methods</i>: This was a retrospective cohort study that included 522 patients. Cox proportional hazards models were used to evaluate the association between PINI and OS along with clinical and hematologic variables. Model performance was assessed using the concordance index (C-index), integrated area under the curve (iAUC), continuous net reclassification improvement (cNRI), integrated discrimination improvement (IDI), nomogram construction, and calibration curves. <i>Results</i>: In the multivariate analysis, the PINI remained an independent predictor of OS, along with age, American Society of Anesthesiologists physical status, stage, pleural invasion, and the modified Shine-Lal index. The full model (FM), incorporating all these variables, outperformed the baseline model (BM) that was based solely on stage (C-index: 0.841 vs. 0.692; iAUC: 0.804 vs. 0.663; both <i>p</i> < 0.001). Compared with the intermediate model (IM), which included all FM variables except the PINI, the FM demonstrated modest but statistically significant improvements (C-index: 0.841 vs. 0.820, <i>p</i> = 0.012; iAUC: 0.804 vs. 0.793, <i>p</i> = 0.001). At 3- and 5-year time points, the FM still yielded superior risk reclassification over the BM and IM, as indicated by improvements in IDI and cNRI. A nomogram based on the FM showed good calibration with the observed survival outcomes. <i>Conclusions</i>: The PINI is an independent and clinically meaningful prognostic biomarker in patients with stage I-IIIA NSCLC undergoing curative surgery. Incorporating the PINI into the BM or IM improved risk discrimination and reclassification, supporting its potential use in personalized prognostic assessment. However, external validation is warranted.