Aim: We evaluated preoperative serum carcinoembryonic antigen (CEA) as a prognostic factor for colorectal cancer and determined when surveillance of this marker was useful.
Methods: Serum CEA was measured preoperatively in 1,263 patients who underwent curative resection for colorectal cancer at 3-month intervals for the first 2 postoperative years and at 6-month intervals thereafter. Mean follow-up was 48 months (range 1-156 months).
Results: The 5-year disease-free survival was less in patients with a high preoperative serum CEA level (P<0.0001). Among patients with a tumor recurrence, 38.5% had high follow-up serum CEA levels. The number of patients with high postoperative serum CEA levels exceeded the number of patients with high preoperative levels. High preoperative and follow-up serum CEA levels were independent prognostic factors for tumor recurrence (P=0.003 and P<0.001, respectively). In patients with high preoperative serum CEA levels, CEA surveillance had a 92.3% positive predictive value (PPV) and a 96.1% negative predictive value (NPV). The mean interval between postoperative serum CEA elevation and the diagnosis of a tumor recurrence [diagnostic interval (DI)] was 2.5 months (range 5-17 months). The DI was 0 in 18.8% of patients with a tumor recurrence.
Conclusion: High serum CEA levels preoperatively and at follow-up are prognostic factors for colorectal cancer. Postoperative serum CEA surveillance is used most effectively when patients have high preoperative serum CEA levels. Considering the DI of 0 in 18.8% of the patients, the current CEA surveillance schedule might be changed.