Who is at Risk?
For the great majority of people, the major factor that increases a person’s risk for colorectal cancer (CRC) is increasing age. Risk increases dramatically after age 50 years; 90% of all CRCs are diagnosed after this age. The history of CRC in a first-degree relative, especially if before the age of 55 years, roughly doubles the risk. Other risk factors are weaker than age and family history. People with inflammatory bowel disease have a much higher risk of CRC. A small percentage (<5%) of CRCs occur in people with a genetic predisposition, including familial adenomatous polyposis and hereditary nonpolyposis coli.