Table 1 Risk categories for colorectal cancer based on family history

Category 1. At or slightly above average risk

Asymptomatic people who have:

• no personal history of bowel cancer, advanced adenoma, or chronic ulcerative colitis, and

• either no close relatives with bowel cancer or one first-degree or second-degree relative with bowel cancer diagnosed at age 55 years or older.

Category 2. Moderately increased risk

Asymptomatic people who have:

• one first-degree relative with bowel cancer diagnosed before the age of 55 years (without the potentially high-risk features listed below for category 3), or

• two first-degree or one first- and one second-degree relative(s) on the same side of the family with bowel cancer diagnosed at any age (without the potentially high-risk features listed below for category 3).

Category 3. Potentially high risk

Asymptomatic people who have:

• three or more first-degree or a combination of first-degree and second-degree relatives on the

same side of the family diagnosed with bowel cancer (suspected HNPCC), or

• two or more first-degree or second-degree relatives on the same side of the family diagnosed with bowel cancer, including any of the following high-risk features:

- multiple bowel cancers in the one person

- bowel cancer before the age of 50 years

- at least one relative with cancer of the endometrium, ovary, stomach, small bowel, renal pelvis, ureter, biliary tract or brain, or at least one first-degree relative with a large number of adenomas throughout the large bowel

(suspected FAP), or

• somebody in the family in whom the presence of a high-risk mutation in the APC (adenomatous polyposis coli) gene or one of the mismatch repair (MMR) genes has been identified.