Screening and genetic counselling for relatives of patients with colorectal cancer in a family cancer clinic.

OBJECTIVE: To introduce and monitor a screening programme for first degree relatives of patients with colorectal cancer based on their calculated lifetime risk.

DESIGN: Lifetime risks were calculated for first degree relatives of patients with colorectal cancer and used to offer screening based on estimated risk.

SETTING: A family cancer clinic was set up as part of the North East Thames Regional Genetic Service for relatives of patients who had developed colorectal cancer before the age of 45 and members of families in which multiple cancer had occurred.

PATIENTS: Self referrals as well as patients referred by general and hospital practitioners.

INTERVENTION: Relatives with a lifetime risk of 1 in 10 or greater (high risk group) were offered screening five yearly by colonoscopy, and those whose risk was between 1 in 10 and 1 in 17 were offered yearly screening for faecal occult blood. Women with family histories compatible with Lynch type II cancer family syndrome were offered screening for breast and pelvic tumours.

RESULTS: In four years 715 patients were seen. Acceptance of screening was 90% (644 patients). Of 151 patients screened for faecal occult blood, two were found to have polyps. This screening test was unsatisfactory for the high risk group, having a negative predictive value of 78% in 59 patients tested. Regular screening by colonoscopy was offered to 382 high risk patients; 62 patients with polyps and five with colonic cancer were found. One hundred and ten pedigrees were identified with the Lynch type II cancer family syndrome, and four of 35 women screened were found to have breast cancer. Of 14 relatives aged over 65 with a 1 in 2 risk of site specific colonic cancer or Lynch type II cancer family syndrome, seven were found to have polyps, one of whom had carcinoma in situ.

CONCLUSIONS: Family history can be used to identify those at risk of colonic cancer and to target appropriate screening. Colonoscopy detected a high number of premalignant colonic polyps, but faecal occult blood testing was unsatisfactory for those at high risk of colorectal cancer.