Faecal occult blood screening of first degree relatives of patients with colorectal cancer.

A full first-degree family history was taken from 161 patients with colorectal cancer (Group 1) and from a group of 203 subjects previously investigated and found to have no colorectal neoplasia (Group 2). Twenty-six (16%) of patients in Group 1 compared with 23 (11%) in Group 2 had at least 1 first-degree relative with colorectal cancer (p = 0.23). Contact of first-degree relatives was possible in 123 patients in Group 1. Of these, 4 were members of 'cancer families' with 26 available first-degree relatives. The remaining 119 patients had 341 contactable first-degree relatives. They were approached by post and offered faecal occult blood (FOB) screening. One hundred and sixty-two (47%) completed FOB tests of which 12 (8%) were positive. Investigation of these individuals detected 4 adenomas. In the subgroup of 20 patients with 1 or 2 first-degree relatives with colorectal cancer, there were 78 potential relatives of whom 71 were contacted. Thirty-two (45%) FOB tests yielded 1 positive found to have an adenoma. A control group of 332 individuals was selected randomly from general practitioners' lists and offered FOB testing. One hundred and fifty-five (47%) complied of whom 7 (4.5%) were positive. Investigation yielded 1 adenoma. Thirteen of the 26 relatives of the 4 'cancer family' patients were investigated by endoscopy and 2 (15%) had large polyps detected. Although there may be an increased risk of colorectal neoplasia in first-degree relatives of patients with sporadic colorectal cancer, this risk is not sufficiently high to justify separate screening.