Prognostic Impact of the Postoperative Carcinoembryonic Antigen Level after Curative Resection of Locally Advanced Rectal Cancer

Objectives: This study was conducted to investigate whether preoperative or postoperative carcinoembryonic antigen (CEA) with a new cut-off value is more optimal for predicting long-term outcomes in patients with Stage II/III rectal cancer, and to investigate the effectiveness of postoperative adjuvant chemotherapy (POAC) based on the CEA values. Methods: Serum CEA levels were measured preoperatively (pre-CEA) and postoperatively (post-CEA). The area under the receiver operating curve (AUROC) was used to determine a cut-off for CEA. The cut-off for CEA relative to recurrence-free survival (RFS) was established as that giving the highest AUROC. In comparison of superiority between pre- and post- CEA levels, Akaike's information criterion (AIC) was used in the Cox proportional-hazard regression model. Results: The subjects were 323 patients who underwent curative surgical treatment for Stage II/III rectal cancer. AIC values indicated that RFS was better stratified by a post-CEA level with a cut-off of 2.3 ng/ml compared with other classifications of pre- or post- CEA. In Stage III or high-risk Stage II cases, there was no effect of POAC on RFS in those with post-CEA <2.3 ng/ml (p=0.39), but in those with post-CEA >= 2.3 ng/ml there was a trend for better RFS in patients who received POAC compared to those without POAC (p=0.06). Conclusions: Patients with post-CEA >= 2.3 ng/ml had worse long-term outcomes compared with those with post-CEA <2.3 ng/ml. Post-CEA with a cut-off of 2.3 ng/ml may be useful in determining the indication for POAC for in Stage III or high-risk Stage II cases.