Prognostic impact of persistent postoperative neutrophil-to-lymphocyte ratio elevation 1 year after colorectal cancer surgery.

Colorectal cancer (CRC) remains a major cause of cancer-related mortality despite advances in screening and treatment. Inflammation plays a key role in tumor progression, with the neutrophil-to-lymphocyte ratio (NLR) emerging as a potential prognostic marker. While preoperative NLR is a well-established predictor of survival, its prognostic value 1 year postoperatively remains underexplored. This study aims to evaluate the prognostic significance of NLR 1 year after curative CRC surgery, identify factors associated with its elevation, and assess its impact on survival and recurrence. A retrospective analysis was conducted on 788 patients who underwent curative-intent CRC surgery between 2015 and 2022. NLR was assessed preoperatively and 1 year postoperatively, using a cutoff of 3.3. Patients were categorized into four subgroups: "Low-Low": NLR ≤ 3.3 pre- and postoperatively; "Low-High": NLR ≤ 3.3 preoperatively but > 3.3 postoperatively; "High-Low": NLR > 3.3 preoperatively but ≤ 3.3 postoperatively, and "High-High": NLR > 3.3 at both time points. Survival analysis was performed using Cox regression. Postoperative NLR values were significantly lower than preoperative levels (median: 2.8 vs. 4.1, p < 0.001). An elevated post-NLR (> 3.3) correlated with poorer survival and higher recurrence rates. The "Low-High" group exhibited the worst prognosis, with a 5-year survival rate of 42.6% compared to 79.8% in the "Low-Low" group. Multivariate analysis confirmed post-NLR > 3.3 as an independent predictor of worse survival (HR: 3.49; 95%CI 2.41-5.04). Persistently elevated NLR 1 year after CRC surgery is associated with worse survival and higher recurrence. Routine postoperative NLR monitoring may help identify high-risk patients for closer follow-up and early intervention.