Preoperative inflammation-based biomarkers and postoperative pulmonary complications after lung resection for lung cancer: a systematic review with selective exploratory quantitative synthesis.

BACKGROUND: Postoperative pulmonary complications (PPCs) remain a source of morbidity after lung resection for lung cancer. Several preoperative inflammation-based biomarkers have been investigated as potential risk indicators, but the literature remains methodologically heterogeneous across biomarker types, analytic scales, and outcome definitions. METHODS: Following PRISMA 2020 guidelines, we searched PubMed, Web of Science, Scopus, Embase, and the Cochrane Library from inception to March 20, 2026. We included original studies evaluating preoperative inflammation-based biomarkers in patients undergoing lung resection for lung cancer if PPCs or extractable pulmonary complication outcomes were reported. PPCs were prespecified as the primary outcome framework, and postoperative pneumonia (POP) was analyzed as a major subtype. Because of substantial heterogeneity across biomarkers, analytical approaches, and outcome definitions, the evidence was synthesized at the study level, with selective exploratory quantitative syntheses performed only when clinical comparability was acceptable. RESULTS: Eight studies were included, comprising seven retrospective cohorts and one prospective cohort. Quantitative synthesis was exploratory because biomarker selection, analytic scale, and pulmonary outcome definitions varied substantially across studies. Pooled analyses based on extractable effect estimates were generally unstable and highly heterogeneous; for example, the biomarker-specific NLR analysis was not significant (OR 1.53, 95% CI 0.79-2.99; I2 = 96%), and the pooled all-estimates analysis remained highly heterogeneous (OR 1.04, 95% CI 1.00-1.08; I2 = 92%). Restriction to adjusted estimates did not materially reduce this inconsistency (OR 1.01, 95% CI 0.97-1.04; I2 = 94%). By contrast, an exploratory dichotomous synthesis of cutoff-defined biomarker categories suggested higher pulmonary risk in patients with elevated preoperative biomarker levels (OR 1.81, 95% CI 1.33-2.47; I2 = 0%), although this result was based on crude data across different biomarkers and should be interpreted cautiously. At the study level, CRP, SII, and NLR showed the most consistent adverse associations. CONCLUSIONS: Selected preoperative inflammation-based biomarkers, particularly CRP, SII, and NLR, may be associated with postoperative pulmonary morbidity after lung cancer resection. However, the literature is dominated by retrospective studies and marked methodological heterogeneity, precluding a single robust pooled inference. Prospective biomarker-specific studies with standardized pulmonary outcome definitions are needed before these markers can be considered for perioperative risk stratification. SYSTEMATIC REVIEW REGISTRATION: https://www.crd.york.ac.uk/PROSPERO/view/CRD420261356969, PROSPERO CRD420261356969.