Family Risk and Genetics in Bowel Cancer

Most bowel cancers are sporadic (happen by chance), but about 1 in 10 cases are linked to inherited genetic factors. Knowing your family risk helps decide whether you should start screening earlier, or consider genetic testing.

Family History

Your risk is higher if:

A first-degree relative (parent, sibling, or child) had bowel cancer.
Multiple relatives on the same side of the family were affected.
A relative was diagnosed at a younger age (before 50).

The closer the relation and the younger the age of diagnosis, the stronger the risk.

Genetic Conditions

Some rare inherited syndromes carry a very high risk:

Lynch Syndrome (HNPCC): Increases lifetime risk of bowel and other cancers.
Familial Adenomatous Polyposis (FAP): Causes hundreds of polyps in the bowel, almost always progressing to cancer without treatment.
MUTYH-associated polyposis (MAP): Similar to FAP but usually fewer polyps.

Genetic Testing

Recommended if your family history suggests an inherited syndrome.
Usually involves a blood test or cheek swab to check for specific gene mutations.
Results help guide personalised screening and prevention plans for you and your relatives.

What This Means for Screening

Average risk: Begin screening at 50 (FIT test, colonoscopy if needed).
Moderate risk: Screening may start at 40, or 10 years earlier than the youngest family diagnosis.
High risk (Lynch, FAP, MAP): Screening may begin in the 20s or 30s, with regular colonoscopy.

Takeaway