Association between neutrophil-to-lymphocyte ratio and risk of immune checkpoint inhibitors-related pneumonitis and radiation pneumonitis in lung cancer: a systematic review and meta-analysis.

BACKGROUND: The prognostic role of neutrophil-to-lymphocyte ratio (NLR) for prediction of risk of immune checkpoint inhibitors-related pneumonitis (CIP) and radiation pneumonitis (RP) in patients with lung cancer remains unclear. This study aimed to clarify the relationship of NLR with the risk of immune CIP and RP among lung cancer patients. METHODS: Web of Science, Embase, PubMed and Chinese National Knowledge Infrastructure (CNKI) databases were searched up to October 27, 2025. Odds ratios (ORs) were combined and subgroup analyses by tumor type [non-small cell lung cancer (NSCLC), lung cancer or small cell lung cancer (SCLC)] and grade of pneumonitis (all grades or grade 3 or higher) were performed. RESULTS: Eleven studies with 2,439 patients were included and 298 (12.2%) patients experienced the CIP and/or RP. For patients receiving concurrent immunotherapy and radiotherapy, NLR was not associated with risk of pneumonitis. Pooled results demonstrated that NLR was not associated with the risk of CIP (OR =1.22, P=0.14) and subgroup analysis by tumor type also manifested negative results. However, elevated NLR was significantly related to the occurrence of severe (grade 3-5) CIP [OR =7.93, 95% confidence interval (CI): 3.51-17.92, P<0.001]. Besides, higher NLR predicted increased risk of RP (OR =2.75, 1.75-4.33, P<0.001) in NSCLC and subgroup analysis by the grade of pneumonitis showed similar positive results (all grades: OR =3.10, P<0.001; grade 3-5: OR =2.36, P=0.01). CONCLUSIONS: Based on above findings, NLR might serve as a predictor for the development of severe CIP in lung cancer and RP in NSCLC. However, more relevant studies are still needed to further clarify the predictive role of NLR for CIP and RP among lung cancer patients.