Preoperative inflammatory and immune-nutritional markers and postoperative pulmonary complications after gastric and colorectal cancer surgery: a systematic review and narrative synthesis.

Background: Postoperative pulmonary complications (PPCs) remain a major source of morbidity after gastrointestinal cancer surgery. A range of preoperative inflammatory and immune-nutritional biomarkers have been proposed as predictors of postoperative pulmonary risk, but the available evidence remains scattered and methodologically heterogeneous. This study aimed to systematically evaluate the association between preoperative inflammatory and immune-nutritional markers and postoperative pulmonary complications after gastrointestinal cancer surgery. Methods: Following PRISMA 2020 guidelines, we systematically searched PubMed, Embase, Web of Science Core Collection, Scopus, and the Cochrane Library from database inception to 3 March 2026. Original observational studies evaluating preoperative inflammatory or immune-nutritional markers in adult patients undergoing surgery for gastrointestinal malignancies were eligible if they reported PPCs, postoperative pneumonia, or other extractable pulmonary complications. The primary outcome was PPCs, while postoperative pneumonia and other individual pulmonary complications were extracted separately when available. Due to substantial heterogeneity in pulmonary outcome definitions, biomarker selection, cutoff determination, and statistical modeling, findings were synthesized narratively. Results: Fifteen studies were included, all of which were observational in design, with overall moderate-to-high methodological quality. Across studies reporting broader PPCs and infectious pulmonary outcomes, adverse preoperative inflammatory and nutritional profiles were generally associated with increased postoperative pulmonary risk. Inflammatory markers such as neutrophil-to-lymphocyte ratio and systemic immune-inflammation index demonstrated the strongest associations in individual studies, while nutritional indicators including albumin, controlling nutritional status score, prognostic nutritional index, and geriatric nutritional risk index consistently indicated an elevated risk in patients with poorer preoperative nutritional status. Overall, the findings pointed to a recurrent pattern of combined inflammatory burden and nutritional impairment rather than reliance on a single biomarker. Because most biomarker-specific findings were supported by single studies and were reported using heterogeneous outcome definitions and analytic scales, formal pooled meta-analysis was not performed. Conclusions: Current evidence suggests that a preoperative double burden of heightened systemic inflammation and impaired nutritional status is associated with increased postoperative pulmonary risk after gastric and colorectal cancer surgery. However, the literature remains heterogeneous in outcome definitions, biomarker modeling, and effect reporting. Standardized prospective studies are needed before these markers can be reliably integrated into perioperative pulmonary risk stratification. Systematic Review Registration: https://www.crd.york.ac.uk/PROSPERO/view/CRD420261361210, identifier CRD420261361210.