EP507 - The Paradoxical Features of Tumor Size in T4 Colon Cancer: A Retrospective Cohort Study

Purpose/Background: Although recent studies have reported that a larger tumor size in colorectal cancer is associated with a better prognosis, this remains a controversial topic. The purpose of this study was to investigate the clinicopathological features and oncologic outcomes according to tumor size in patients with T4 colon cancer.

Methods/Interventions: We retrospectively analyzed patients who underwent curative resection for pathologically confirmed T4 colon cancer at a tertiary center from January 2010 to December 2016. A receiver operating characteristic (ROC) curve analysis was performed to determine the optimal cut-off value for tumor size. Based on this cut-off, clinicopathologic patterns, overall survival (OS), and recurrence-free survival (RFS) were analyzed.

Results/Outcomes: A total of 421 patients with T4 colon cancer were included in the analysis. There was a significant difference in tumor size between node-negative and node-positive patients (7.0 cm ± 2.8 vs. 5.4 cm ± 2.1, p < 0.001). Following ROC curve analysis, patients were stratified into two groups (tumor size ≥7 cm and < 7 cm). Patients with a tumor size ≥7 cm had a significantly higher proportion of node-negative status (62.6% vs. 32.8%, p < 0.001) and a higher incidence of MSI-H tumors (27.5% vs. 7.9%, p < 0.001). A tumor size of 7 cm or greater was identified as a significant protective factor against lymph node metastasis in the logistic regression model (OR, 0.45; 95% CI, 0.27-0.77; p = 0.003). When comparing oncologic outcomes, there was no difference in 5-year overall survival between the groups (85.5% vs. 79.3%, p = 0.133). However, the 5-year recurrence-free survival was significantly higher in patients with tumors ≥7 cm compared to those with tumors < 7 cm (78.5% vs. 67.8%, p = 0.026). In the Cox regression analysis for 5-year RFS, a tumor size ≥7 cm was not an independent risk factor (HR 0.92, 95% CI 0.57-1.50, p = 0.749).

Conclusion/Discussion: In patients with T4 colon cancer, a larger tumor size was paradoxically associated with improved recurrence-free survival. This survival benefit is likely attributed to the higher incidence of favorable prognostic features, such as node-negative and MSI-high status, rather than tumor size being an independent prognostic factor.

Table 1. Clinicopathological characteristics by tumor size
Data are presented as mean ± SD for continuous measures and n (%) for categorical measures;

CEA, carcinoembryonic antigen; MIS, minimally invasive surgery; MSI-H, microsatellite instability-high


Figure 1. (a) Overall survival by tumor size (b) Recurrence-free survival by tumor size