Perioperative changing patterns of systemic immune-inflammatory index (SII) and outcomes in stage I-III non-small...

The systemic immune-inflammation index (SII) has shown prognostic value in cancers, but its dynamic perioperative changes and implications in non-small cell lung cancer (NSCLC) remain underexplored. This study investigates the prognostic significance of perioperative SII changing patterns in resectable stage I-III NSCLC.

A retrospective cohort of 2,489 patients undergoing curative resection for stage I-III NSCLC [2013-2018] was analyzed. SII (neutrophils × platelets/lymphocytes) was measured preoperatively, postoperatively, and serially over 12 months. Restricted cubic splines (RCS) and X-tile determined optimal SII cutoffs. Latent class growth mixed models (LCGMMs) identified longitudinal SII trajectories. Associations with recurrence-free survival (RFS) and overall survival (OS) were evaluated using Cox models.

High preoperative SII (>50.4), elevated postoperative/preoperative SII ratio (>2.3), and persistent postoperative SII elevation independently predicted worse RFS [adjusted hazard ratios (HRs): 1.37, 1.76, and 2.46, respectively; all P<0.05]. Three distinct SII trajectories emerged: slow-decreasing (93.7%, 3-year RFS 74.4%), sharp-decreasing (4.0%, 3-year RFS 42.0%), and rising (2.31%, 3-year RFS 43.2%). The rising trajectory group exhibited bimodal SII peaks at 2-3 and 8-12 months postoperatively, correlating with a 2.46-fold increased recurrence risk [95% confidence interval (CI): 1.50-4.03; P<0.001] compared to the slow-decreasing group, even after adjusting for preoperative SII and clinicopathological factors.

Perioperative SII changing patterns provide critical prognostic insights beyond static measurements and demonstrate potential for predicting postoperative recurrence risk in stage I-III NSCLC patients.