Pan-Cancer Evaluation of the Neutrophil-to-Lymphocyte Ratio for Survival Prediction: Emphasis on Brain, Lung, Gastric, Colorectal, Liver, and Breast Cancers

Background Systemic inflammation shapes cancer outcomes. We examined the neutrophil-to-lymphocyte ratio (NLR) across common malignancies and built a pragmatic model for survival prediction. Methods From the INSCOC registry, 14,425 patients with lung, gastric, colorectal, liver, brain, or breast cancer were included and randomly split (10,098/4,327) into training and validation sets. Six inflammation-based indices from neutrophil, lymphocyte, and platelet counts were compared for overall survival (OS) using Harrell’s C-index and time-dependent ROC. Associations between NLR and OS were tested by Kaplan–Meier curves, restricted cubic splines, and multivariable Cox models adjusted for demographic, clinical, and treatment factors. A nomogram combining NLR with significant covariates was developed and internally checked by calibration and decision-curve analysis (DCA). Results NLR showed the best discrimination across all six cancers (C-index ~ 0.53–0.63). A threshold of 3.38 identified patients with markedly shorter OS in both sets (log-rank P < 0.001). The risk rose nearly linearly with higher NLR and remained significant after full adjustment. Findings were consistent across age, sex, comorbidity, and treatment strata. The NLR-based nomogram produced accurate, well-calibrated 1-, 3-, and 5-year predictions and yielded greater net benefit on DCA. Conclusions Elevated NLR independently signals worse survival across major solid tumors and outperforms other inflammation-derived indices. The resulting nomogram offers a simple tool to refine individualized risk beyond traditional staging.