Preoperative platelet immune index as a prognostic marker for colon cancer: A comparative analysis of blood-derived indices

Background Multiple immune-inflammatory blood indices have been proposed for colon cancer prognostication; however, comparative evaluations of these indices remain limited. We systematically compared these indices and assessed the prognostic performance of a platelet-monocyte-lymphocyte combination. Methods In a discovery cohort of 2,993 patients, we compared multiple immune-inflammatory indices constructed from platelet, neutrophil, monocyte, and lymphocyte counts. The index with the highest relative relevance in a generalized boosted regression model (GBM) was selected. An independent cohort of 1,124 patients was used for validation. The outcomes included overall survival (OS) and progression-free survival (PFS). Results Regarding GBM analysis, the platelet immune index (PII), calculated as (platelet count × monocyte count) / lymphocyte count, showed the highest relative influence for survival prediction among the tested indices. Using a data-derived cutoff of 80.0, high PII score (≥ 80.0) was associated with worse 5-year OS (64.3% vs. 84.8%, P  < 0.001) and PFS (52.6% vs. 76.2%, P  < 0.001). Using multivariable analysis adjusting for established prognostic factors, high PII values remained independently associated with worse OS (hazard ratio [HR], 1.474; 95% confidence interval [CI], 1.269–1.714) and PFS (HR, 1.422; 95% CI, 1.240–1.630). The findings were validated in the independent cohort. Conclusions Preoperative PII demonstrated independent prognostic value in patients with colon cancer and might aid in risk stratification, particularly within the same TNM stage. High PII score warrants closer postoperative surveillance and consideration in treatment planning.