Taking a Genetic Family History - The Conversation (Bowel Cancer)

Genetics and Bowel cancer

Bowel cancer, also known as colorectal cancer, can have genetic components. While most cases of bowel cancer are sporadic, meaning they occur by chance and are not directly inherited, about 5-10% of cases have a hereditary component.

Hereditary conditions and bowel cancer

There are several hereditary conditions associated with an increased risk of developing bowel cancer, including:

1. Familial adenomatous polyposis (FAP): This is a rare genetic condition caused by mutations in the APC gene. People with FAP develop hundreds or thousands of polyps in the lining of their colon and rectum, usually starting in their teens or twenties. Without treatment, FAP almost always leads to colorectal cancer.
2. Lynch syndrome (also known as hereditary non-polyposis colorectal cancer or HNPCC): This is the most common inherited form of colorectal cancer, accounting for about 3-5% of cases. Lynch syndrome is caused by mutations in genes involved in DNA mismatch repair, such as MLH1, MSH2, MSH6, and PMS2. Individuals with Lynch syndrome have a significantly increased risk of developing colorectal cancer, as well as other cancers including endometrial, ovarian, stomach, small intestine, urinary tract, and others.
3. MUTYH-associated polyposis (MAP): This condition is caused by mutations in the MUTYH gene and is associated with an increased risk of developing multiple colorectal polyps and cancer.
4. Other rare hereditary syndromes: There are several other rare genetic conditions associated with an increased risk of colorectal cancer, including Peutz-Jeghers syndrome, juvenile polyposis syndrome, and Cowden syndrome, among others.

In addition to these specific genetic syndromes, having a family history of colorectal cancer (especially if it's diagnosed at a young age or if multiple family members are affected) can also increase an individual's risk of developing the disease, although the specific genetic factors involved may not always be known.

It's important for individuals with a family history of bowel cancer or any of these hereditary conditions to undergo genetic counseling and testing, as well as regular screening for colorectal cancer, to help detect and manage their risk. Early detection through screening can significantly improve outcomes for individuals at high risk of developing colorectal cancer.