Background: Carcinoembryonic antigen (CEA) is the most widely used tumor marker in colon cancer; however, there has been controversy regarding the significance of preoperative serum CEA level as a prognostic factor for recurrence. In this study, we evaluated the optimal cutoff value and prognostic significance of preoperative serum CEA level in stage III colon cancer. Methods: Based on a retrospective cohort of 965 patients with stage III colon cancer who underwent elective curative surgery and adjuvant chemotherapy with fluoropyrimidine and oxaliplatin (training set), we determined the optimal cutoff value of CEA for recurrence using the Contal and O’Quigley method. We assessed the prognostic value of this cutoff value in terms of disease-free survival (DFS) and overall survival (OS) in a prospective cohort of 268 patients with stage III colon cancer (validation set). A Cox proportional hazards model was used to explore the association of prognostic variables with DFS and OS. Results: The statistically determined best cutoff value for CEA was 3 ng/mL in the training set. A high CEA level (≥3 ng/mL) was associated with inferior DFS (hazard ratio [HR] 4.609, 95 % confidence interval [CI] 2.028–10.474) and OS (HR 3.956, 95 % CI 1.127–13.882) in the validation set, while multivariate analysis showed that a high CEA level was an independent risk factor for DFS and OS in both study subsets. Conclusion: Preoperative serum CEA level is an independent prognostic factor for DFS and OS in patients with stage III colon cancer after curative resection and adjuvant chemotherapy.
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