Antitumor immune response to colorectal cancer antigen detected by the leukocyte adherence inhibition test (LAI) in groups at high risk for colorectal cancer.

Colorectal cancer is the second leading cause of cancer death in western populations. As treatment outcome is highly correlated with stage at diagnosis, early detection is a very important task. Three high-risk groups for colorectal cancer (first-degree relatives of colorectal cancer patients; individuals with past history of colorectal neoplasms, polyps, or carcinoma; and patients with ulcerative colitis) were screened for colonic neoplasms. The study program included the leukocyte adherence inhibition test (LAI), a specific immune response test for colorectal cancer antigen; fiberoptic sigmoidoscopy or colonoscopy; and guaiac impregnated slide test. The main finding was the detection of 92 positive LAI tests out of 451 high-risk individuals tested (20%), compared to eight positive tests out of 194 (4.1%) in a control group. Fifty-six colonic neoplasms were found out of 344 (16%) colonoscopies performed, most of them adenomatous polyps and a few carcinomas. Our findings, compared with the expected 2-3% neoplasms in low-risk groups, would prove that the screenees were indeed at high risk. However, only 11/56 (19%) of the polyps identified were LAI positive. The number of polyps found among LAI positive individuals were, so far, 11/92 (11%). The guaiac impregnated slide test for occult blood in the stool was performed in 221 screenees. Of these only 10 were positive (4.5%) compared with the average of 1% positive tests in low-risk groups.