High postoperative carcinoembryonic antigen as an indicator of high-risk stage II colon cancer

Postoperative carcinoembryonic antigen (post-CEA) has recently been reported to be a reliable prognostic factor for colon cancer. However, most clinicians decide whether or not to conduct adjuvant chemotherapy (AC) for stage II colon cancer according to major guidelines, which do not include post-CEA in their high-risk criteria. The present study aimed to assess post-CEA in stage II colon cancer for which the significance of AC is unknown. The present study analyzed 199 consecutive patients with stage II colon cancer who underwent curative surgery between January 2007 and December 2016. The CEA value was considered high when it was ≥5.0 ng/ml. The prognostic value of high post-CEA values was assessed. Overall, 19 patients exhibited high post-CEA levels. Kaplan-Meier survival curve analysis demonstrated that patients with high post-CEA levels had significantly worse relapse-free survival (RFS) and overall survival (OS) than those with normal post-CEA [RFS, 63.5 (high post-CEA) vs. 88.0% (normal post-CEA), P=0.003; OS, 76.5 (high post-CEA) vs. 96.8% (normal post-CEA), P<0.001]. Multivariate analysis demonstrated that high post-CEA remained a significant independent risk factor for worse RFS [hazard ratio (HR), 3.98; P=0.006]. The same was also demonstrated for patients without AC (HR, 5.43; P=0.008). To the best of our knowledge, the present study was the first to demonstrate that high post-CEA levels may be an indicator of high-risk stage II colon cancer, even for patients without AC. These results highlight the need for a multicenter prospective study.