The detection of colorectal carcinomas with the use of CA-50 radioimmunoassay inhibition test.

A radioimmunoassay was used for the detection of the human carcinoma-associated antigen CA-50 in the serum of 50 normal subjects, 16 patients with inflammatory bowel diseases and 77 patients with primary and secondary colorectal carcinomas. Serum levels in all normal patients and those with benign disease were below 17 U/ml, while 40 of 77 (51%) patients with carcinoma had levels above 17 U/ml. The sensitivity of this test was 22% for Dukes' A carcinoma, 29% for Dukes' B, 59% for Dukes' C and 73% for metastatic disease. The CA-50 levels were elevated in 7 of 9 (78%) patients who developed tumour recurrence following curative surgery compared with 15 of 43 (35%) patients who are alive and tumour free (p less than 0.05). Therefore, this test may prove useful in the diagnosis and prognosis of patients with colorectal carcinomas.