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Issues concerning the impact of predictive genetic testing on colonoscopic surveillance in an extended family with hereditary non-polyposis colorectal cancer (HNPCC) are discussed. Predictive genetic testing ensures that many individuals can be withdrawn from regular colonoscopic surveillance.

* Objective: To quantify any risk for colorectal cancer in first-degree relatives of patients with common colorectal cancer and to define possible markers for increased risk. * Design: Case-control family study. * Patients: Relatives of colorectal cancer patients and of matched control patients from a one-surgeon practice. * Mothods: Family medical histories were obtained for 7493 first-degree relatives and 1015 spouses of 523 case-control pairs. Reported diagnoses of colorectal cancer in relatives were verified in 79% of instances. * Results: By case-control analysis, the odds ratio was 1.8 (95% Cl, 1.2 to 2.7) for one and 5.7 (Cl, 1.7 to 19.3) for two affected relatives. By matched analysis of risk in relatives, the increased risk to parents and siblings was 2.1 times greater for case patients than for control patients (Cl, 1.4 to 3.1); 3.7 times greater (Cl, 1.5 to 9.1 ) with case patients diagnosed before 45; and 1.8 times greater (Cl, 1.2 to 2.9) with case patients diagnosed at 45 years or older; and was independent of gender, type of relative, site of cancer, and type of cancer (single or multiple). The cumulative incidence among first-degree relatives was greater for case patients than for control patients (P < 0.001), and in case patients, greater for those diagnosed before 55 years of age (P < 0.001). The cumulative incidence ([+ or -] S.E.) to age 80 was 11.1% [+ or -] 1.3%, 7.3% [+ or -] 0.8%, and 4.4% [+ or -] 1.0% among relatives of case patients diagnosed before age 45 years, between 45 and 54 years, and at 55 years or older, respectively, and was 2.4% [+ or -] 0.6% in relatives of control patients. * Conclusions: First-degree relatives of patients with common colorectal cancer have an increased risk for colorectal cancer. This risk is greater if diagnosis was at an early age and is greater when other first-degree relatives are affected. This increased risk should be considered when formulating screening strategies., First-degree relatives of patients with common colorectal cancer may have a higher risk of developing this type of cancer than other individuals. A study compared the incidence of colorectal cancer among 7,493 first-degree relatives and 1,015 spouses of 523 colorectal cancer patients and 523 healthy individuals. The risk of developing colorectal cancer was twice as high for parents and siblings of colorectal cancer patients than for those of healthy individuals. This risk was higher for individuals with two first-degree relatives with colorectal cancer than for those with only one. The cumulative risk was higher among first-degree relatives of patients who were under 45 years old at the time of diagnosis. First-degree relatives of colorectal cancer patients should consider having routine screening for colorectal cancer beginning at the age of 40 years old.