Preoperative serum levels of CEA and CA 242 in colorectal cancer.

Preoperative serum levels of CEA and CA 242 were determined in 260 patients with colorectal cancer and in 92 patients with benign colorectal diseases. The overall sensitivity of the CEA test was 43% and of the CA 242 test 39%. The corresponding specificities were 90% and 87% respectively, using 5 ng ml-1 as cut-off level for CEA and 20 U ml-1 for CA 242. The sensitivity of CEA was 26%, 32%, 38% and 77% for Dukes A, B, C and D colorectal cancer, and the sensitivity of CA 242 was 26%, 26%, 40% and 67%, respectively. The correlation between CEA and CA 242 was low. Concomitant elevation of both markers was seen in 5%, 12%, 18% and 59% of patients with Dukes A, B, C and D colorectal cancer, respectively. Of all the patients, 23% showed elevation of both the CEA and the CA 242 level, whereas CEA alone was elevated in 20% and CA 242 alone in 15% of the patients with colorectal cancer. Combined use of both markers raised the overall sensitivity from 43% to 58%, but reduced the specificity from 90% to 80%. The increase in sensitivity by combining the two markers was most marked in Dukes A, B and C colorectal cancer. Either or both of the markers were elevated in 46%, 46% and 60% of the patients respectively. The clinical value of combining CEA and CA 242 seems very promising and should be further investigated in prospective studies.