Increased Systemic Immune-Inflammatory Index and Association with Occult Nodal Disease in Non–Small Cell Lung Cancer

BACKGROUND: It has been proposed that more aggressive tumors trigger a stronger inflammatory response than less aggressive types. We hypothesize that systemic immune-inflammatory index (SII) is associated with occult nodal disease (OND) in clinically node-negative patients undergoing lung resection for non–small cell lung cancer (NSCLC). STUDY DESIGN: The study included patients who underwent lung resection with nodal dissection, according to current guidelines, at a single center between 2010 and 2021 for NSCLC. Preoperative SII within 3 weeks of surgery was calculated. OND was defined as a clinically node-negative patient found to be pathologically node-positive. Cut-point analysis for SII was performed to identify the level most strongly associated with OND. Univariable and multivariable logistic regressions were used to examine the association between SII, clinical factors, and OND. RESULTS: A total of 199 patients met inclusion criteria, of whom 51% (102 of 199) were women. The median number of nodes and nodal stations examined was 13 (interquartile range 9 to 17) and 6 (interquartile range 5 to 6), respectively. The cut point was determined to be SII 112 or more. On univariable analysis, high SII was associated with OND (odds ratio 15.75, 95% CI 2.09 to 118.73, p = 0.007). On multivariable analysis, after controlling for age, BMI, approach, sex, smoking history (pack-years), forced expiratory volume in 1 second, performance status, comorbidity, histology, lymphovascular invasion, tumor differentiation, and tumor size, high SII was associated with OND (odds ratio 34.59, 95% CI 2.69 to 444.88, p = 0.007). CONCLUSIONS: Increased SII is associated with OND in patients undergoing lung resection for NSCLC.