Which hereditary factors increase the risk of rectal cancer?

Updated: Apr 06, 2021
  • Author: Burt Cagir, MD, FACS; Chief Editor: N Joseph Espat, MD, MS, FACS  more...
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The relative risk of developing colorectal cancer is increased in the first-degree relatives of affected patients. For offspring, the relative risk is 2.42 (95% confidence interval [CI]: 2.20-2.65); when more than one family member is affected, the relative risk increases to 4.25 (95% CI; 3.01-6.08). If the first-degree family member is younger than 45 years at the time of diagnosis, the risk increase is even higher. [31]

Regarding the personal history of colorectal cancer or polyps: Of patients with colorectal cancer, 30% have synchronous lesions, usually adenomatous polyps. Approximately 40-50% of patients have polyps on a follow-up colonoscopy. Of all patients who have adenomatous polyps discovered via a colonoscopy, 29% of them have additional polyps discovered on a repeat colonoscopy one year later. Malignancy develops in 2-5% of patients. The risk of cancer in people who have had polyps removed is 2.7-7.7 times that of the general population. [32]

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