Differences in serum tumor markers between colon and rectal cancer. Comparison of CA 242 and carcinoembryonic antigen.

PURPOSE

We investigated whether there are differences in serum levels of CA 242 and carcinoembryonic antigen (CEA) between patients with colon and rectal cancer.

METHODS

Preoperative serum levels of CA 242 and CEA were determined in 153 patients with colon cancer and in 107 patients with rectal cancer.

RESULTS

At the recommended cut-off levels for CA 242 and CEA, the overall sensitivity of CA 242 was 39 percent for both colon and rectal cancer, whereas the sensitivity of CEA was 40 percent for colon and 47 percent for rectal cancer. A combination of CA 242 and CEA increased overall sensitivity to 57 percent in colon cancer and to 62 percent in rectal cancer, whereas specificity decreased by 10 percent, compared with CEA alone. In colon cancer either or both markers were elevated in 38, 46, 56, and 84 percent of patients with Dukes Stages A, B, C, and D, respectively. Corresponding figures for rectal cancer were 52, 46, 71, and 87 percent, respectively.

CONCLUSIONS

CA 242 showed equal sensitivity for colon and rectal cancer. In Stages A, C, and D, sensitivity of CEA and of a combination of CEA and CA 242 was higher in rectal than in colon cancer, but the difference was not significant. Concomitant use of markers increased sensitivity sharply compared with use of a single marker both in colon and rectal cancer.