Incorporation of serum carcinoembryonic antigen levels into the prognostic grouping system of colon cancer.

PURPOSE: This study aimed to clarify the significance of preoperative serum carcinoembryonic antigen (CEA) on disease-free survival (DFS) in colon cancer and propose a new prognostic grouping system.

METHODS: A multiinstitutional retrospective cohort of 7296 colon cancer patients who underwent R0 surgery between 1997 and 2006 was analyzed. We stratified preoperative serum CEA values into three categories (C-stages): C0 (normal CEA), C1A (up to double the cutoff value), and C1B (more than double the cutoff value) and stratified each TNM stage by C-stage. Multivariate analyses using Cox regression models were used to analyze the significance of C-stage on 5-year DFS.

RESULTS: CEA level was an independent factor affecting DFS; the 5-year DFS of patients with C0 and C1, as well as those with C1A and C1B, differed significantly (C0 84.6%, C1 69.8%, C1A 72.7%, and C1B 66.4%, P < 0.0001). Additionally, the DFS of pStages IIC and C1B was significantly lower than of pStages IIIA and C0 (65.8 vs. 87.7%, respectively; hazard ratio 3.44, 95% confidence interval 1.97-5.88, P < 0.0001). Moreover, the 5-year DFS of pStages IIIA and C0 or C1A did not differ significantly from pStages I and C1A (87.7 vs. 87.7%, P = 0.90 and 86.4 vs. 87.7%, P = 0.78, respectively).

CONCLUSIONS: pStage IIC and C1B disease should be considered candidates for intensive adjuvant chemotherapy. Conversely, pStages IIIA and C0 or C1A could be exempted from adjuvant chemotherapy. Incorporating C-stage into the current TNM staging system may facilitate decision making regarding the use of adjuvant chemotherapy in colon cancer patients.