Differences in carcinoembryonic antigen levels between colon and rectal cancer

The aim of the present study was to investigate the levels of the serum tumor biomarker carcinoembryonic antigen (CEA) in patients with carcinoma of the colon and rectum in different clinical stages. Colorectal cancer (CRC) is one of the most commonly diagnosed types of cancer worldwide and previous studies have reported rapidly updated therapeutic regimes. While the majority of studies focus on CRC as a single entity, certain studies distinguish colon cancer (CC) from rectal cancer (RC), as there is a hypothesis stating that CC and RC are two naturally different entities. CEA is reported to be an important tumor-associated antigen overexpressed in CRC, which is routinely detected as a significant indicator of CRC. Our study aimed to identify potential differences in the expression of CEA between CC and RC, which may, to some degree, reflect the natural differences between the two. We investigated 240 CRC cases between July, 2010 and December, 2012 from The First and Second Affiliated Hospitals of Dalian Medical University, including 117 CC and 123 RC patients with tumors classified by Duke's staging as A-D. The serum CEA level was measured preoperatively by radioimmunoassays as a routinely used auxiliary indicator. The expression of CEA differed between CC and RC, with the former exhibiting variation among the four stages, whereas no variation was observed in RC. In addition, there were differences between CC and RC regarding the CEA level in stage C and D. Furthermore, the CEA level in stage C of CC was significantly lower compared to that in any other stage. In conclusion, the intrinsic distribution of the CEA level between CC and RC suggests that CC and RC may be two naturally different entities; the significantly low CEA level in stage C of CC indicates that stage C may be crucial in the evolution of CC.