Background: The risk for colorectal cancer among family members of patients with colorectal cancer is well established, but the risk among family members of patients with colorectal adenomas is less well established.
Objective: To examine the risk for colorectal cancer among first-degree relatives of patients with adenoma compared with that among first-degree relatives of controls without adenoma.
Design: Reconstructed cohort study.
Setting: Three university-based colonoscopy practices in New York City.
Patients: 1554 first-degree relatives of 244 patients with newly diagnosed adenomas and 2173 first-degree relatives of 362 endoscopically normal controls.
Measurements: Structured interviews were used to obtain family history. Adjusted relative risks (RR) were estimated from Cox proportional hazards regression models.
Results: The risk for colorectal cancer was elevated (RR, 1.74 [95% CI, 1.24 to 2.45]) among first-degree relatives of patients with newly diagnosed adenomas compared with the risk among first-degree relatives of controls. This increased risk was the same for parents (RR, 1.58 [CI, 1.07 to 2.34]) and siblings (RR, 1.58 [CI, 0.81 to 3.08]). First-degree relatives of patients with adenomas did not have elevated risk for other cancers. The risk for colorectal cancer among family members increased with decreasing age at diagnosis of adenoma in probands. Among first-degree relatives of patients who were 50 years of age or younger when the adenoma was diagnosed, the risk was more than four times greater (RR, 4.36 [CI, 2.24 to 8.51]) than that among first-degree relatives of patients who were older than 60 years of age when the adenoma was diagnosed.
Conclusions: First-degree relatives of patients with newly diagnosed adenomas, particularly of patients who are 50 years of age or younger at diagnosis, are at increased risk for colorectal cancer and should undergo screening similar to that recommended for relatives of patients with colorectal cancer.