Relative(s) with bowel cancer
About 70% of people who develop bowel cancer have no family history of the disease.
However, for around 30% of all bowel cancer cases diagnosed there is a family history, hereditary contribution or a combination of both.
Generally speaking, the more members of the family affected by bowel cancer, and the younger they were at diagnosis, the greater the chance of a family link.
Genetic mutations have been identified as the cause of inherited cancer risk in some bowel cancer–prone families; these mutations are estimated to account for only 5% to 10% of bowel cancer cases overall.
What is my risk of hereditary bowel cancer?
The following may help you and your GP assess your personal risk -
High Bowel Cancer Risk
- Relatives diagnosed with Familial Adenomatous Polyposis (FAP)
- Relatives diagnosed with Lynch Syndrome (HNPCC)
- Siblings of people with MUTYH-associated polyposis (an autosomal recessive condition)
Significant family history of bowel cancer
- One first-degree and ≥2 first- or second-degree relatives with bowel cancer on the same side of the family, or
- One first-degree and ≥1 first- or second-degree relatives with bowel cancer on the same side of family in the context of:
- Multiple bowel cancers in one person
- Bowel cancer diagnosed under age 50
- Other HNPCC related cancers
Moderate Bowel Cancer Risk
Family history of bowel cancer
- One first-degree relative diagnosed with bowel cancer under age 55, or
- Two first- or second-degree relatives on the same side of the family diagnosed with bowel cancer at any age
Personal health history
- Bowel cancer
- Special types of polyps, called adenomas
- Inflammatory bowel disease such as ulcerative colitis or Crohn's disease
Average or Slightly Above Average Bowel Cancer Risk
- Age 50 or over; and
- No symptoms to suggest bowel cancer; and
- No family history, up to those with one affected first-degree relative diagnosed with bowel cancer aged 55 or over
A first-degree relative can be a parent, brother, sister or child.
A second-degree relative can be an aunt, uncle, grandparent, grandchild, niece, nephew, or half-brother or half-sister.