Abstract
PURPOSE: To make a Stage II colorectal cancer (CRC) sub-classification based on clinicopathological factors. METHODS: The subjects of this study were 422 patients with Stage II CRC, who underwent curative surgery with dissection of more than 12 lymph nodes. We used the logistic regression analysis or model and Cox's proportional hazard regression model for analysis. RESULTS: Preoperative carcinoembryonic antigen (CEA) level (p = 0.0057), macroscopic type (p = 0.0316), and depth of invasion (p = 0.0401) were extracted as independent risk factors for recurrence, whereas the preoperative CEA level (p = 0.0045) and depth of invasion (p = 0.0395) were extracted as independent predictors of 5-year disease-free survival. We defined depth of invasion (pT4) and the preoperative CEA level (abnormal) as risk factors for recurrence, and classified Grade A as a normal CEA level regardless of depth invasion, Grade B as depth of invasion to pT3 and an elevated CEA level, and Grade C as depth of invasion to pT4 and an elevated CEA level. There were significant differences in cumulative 5-year disease-free survival rates among each grade (Grade A vs. Grade B, p = 0.0474; Grade A vs. Grade C, p < 0.0001; Grade B vs. Grade C, p = 0.0134). CONCLUSION: The sub-classification of Stage II CRC, according not only to depth of invasion but also to preoperative CEA level, is important for predicting the prognosis.