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Table 1 Risk categories for colorectal cancer based on family history

From: Improving adherence to surveillance and screening recommendations for people with colorectal cancer and their first degree relatives: a randomized controlled trial

Risk Category Characteristics
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.
  1. • The above definitions are based on the National Health and Medical Research Council's clinical practice guidelines [3].