Smaller tumor size is associated with poor survival in stage II colon cancer: An analysis of 7,719 patients in the SEER database.

BACKGROUND: We hypothesized that in patients with colon cancer showing heavy intestinal wall invasion without lymph node metastasis (stage II), small tumor size would correlate with more aggressive tumor behaviors and thus poorer cancer-specific survival (CSS).

METHODS: We analyzed Caucasian patients with stage II colon cancer based on data from the US Surveillance, Epidemiology, and End Results (SEER) database. Survival was analyzed using the Kaplan-Meier method, and the log-rank test was used to identify differences. Risk factors were analyzed using the Cox proportional hazard model.

RESULTS: A total of 7719 stage II colon cancer patients from the SEER database were included in the analysis. The cutoff value (5.0 cm) was determined using the X-tile program. The Kaplan-Meier analysis showed that tumors <5.0 cm had a poorer CSS compared to tumors ≥5.0 cm (p = 0.006). Multivariate analysis indicated that tumor size is an independent prognostic factor for stage II patients, and compared to tumors <5.0 cm, tumors ≥5.0 cm were more likely to result in a better CSS (HR 0.775, 95% CI 0.691-0.870, p < 0.001). Tumor size was also analyzed as a continuous variable in the multivariate analysis, and the CSS decreased with decreasing tumor size (HR 0.958, 95% CI 0.936-0.981, p < 0.001). Subgroup analyses suggested that tumor size is also an independent prognostic factor for stage IIA (p = 0.002) and IIC (p < 0.001) patients.

CONCLUSIONS: Smaller tumor size is associated with poor CSS in the stage II colon cancer and particularly in the stage IIA and IIC subgroups.