Genetic testing for bowel cancer

Because bowel cancer can run in families, genetic screening may be recommended to check a person's risk of developing the disease.

Around 1 in 5 people with bowel cancer will have a close relative who also had bowel cancer.

In addition, two rare genetic conditions can cause bowel cancer:

• Familial adenomatous polyposis (FAP)
• Hereditary non-polyposis colorectal cancer, HNPCC, or Lynch syndrome

Genetic tests for FAP check for an APC genetic mutation, while for HNPCC, the mismatch repair (MMR) genes MSH2 and MLH1 are tested.

The Human Fertilisation and Embryology Authority (HFEA) allows screening of embryos for FAP so only those testing negative for the genes are implanted during IVF procedures.

Should I be tested for a gene mutation?

Risk assessment studies suggest that any person of Ashkenazi Jewish descent may consider genetic counselling and testing if there is a personal or family history of colon cancer or pre- cancerous polyps. People of Ashkenazi Jewish descent without a family history of colorectal cancer may want to consider genetic counselling to determine the value of testing, given their circumstances.

How should I interpret the results?

A positive test result means that you have an increased risk of developing colorectal cancer in your lifetime. If you already have had colon cancer or polyps, it may affect screening recommendations. This test does not detect the presence of cancer or polyps.

If you test negative for this gene variant, it means that you do not have this specific cancer risk. But, you may still have a mutation in another gene that causes hereditary colon cancer. Risk may be evaluated through genetic counselling, where family history, lifestyle, and other issues may be discussed.

What should I do if I test positive for the gene variant?

Early diagnosis is important for preventing bowel cancer. Doctors may recommend bowel cancer screening to be done more often or genetic counselling and further testing.