Colon Cancer
What is the chance to develop colon cancer?
What causes colon cancer?
Can colon cancer be inherited?
How do you know if someone has an inherited risk for cancer?
How can I learn about my genetic risk for colon cancer?
What should I expect when I call the Genetics Department?
How can I prepare before contacting the Genetics Department?
What is the chance to develop colon cancer?
Anyone can develop colon cancer. It is the third most common cancer diagnosis. The lifetime risk of colon cancer is about 1 in 20, or about 5%.
What causes colon cancer?
Colon cancer is due to harmful changes (mutations) in genes that control cell growth in the colon. Most genetic changes happen randomly over a lifetime and are not inherited.
Can colon cancer be inherited?
Cancer is not inherited, but you can inherit a genetic risk for cancer. Changes in a cancer risk gene can make a person more likely to develop cancer. About 5% to 10% of people with colon cancer have an inherited cancer risk due to a change in a cancer risk gene.
For more information:
- Hereditary Colon Cancer: Should you have genetic testing?
- Hereditary Cancer Risk: Who should be tested first?
Two conditions cause most cases of hereditary colon cancer:
- Lynch syndrome (also called HNPCC or hereditary non-polyposis colon cancer)
Lynch syndrome is the most common cause of inherited colon cancer risk. There are several genes that can cause Lynch syndrome. A harmful change (mutation) in any Lynch syndrome gene raises the chance to develop colon cancer and other cancers. Cancers seen in families with Lynch syndrome can include:
o Colon cancer diagnosed at young ages (before age 55)
o Uterine or ovarian cancer
o Cancers of the stomach, kidney, urinary tract, brain, small intestine, or pancreas
For more information: Lynch syndrome
- Familial Adenomatous Polyposis (FAP)
FAP accounts for about 1 in every 100 colon cancers. It is caused by a genetic change in a gene called APC. People with "classic" FAP develop hundreds of polyps in the colon and other parts of the gastrointestinal (GI) tract. Without surgery, the polyps eventually lead to cancer. Polyps can start forming in the teens or 20s, so cancer screening needs to start in childhood. There is also a milder form of FAP with fewer polyps and later onset of cancer.
For more information: Familial Adenomatous Polyposis (FAP) syndrome
How do you know if someone has an inherited risk for cancer?
The cancer history in a family can suggest the possibility of inherited cancer risk. Genetic testing can be done to look for harmful changes in many cancer risk genes.
- Colorectal Cancer: Immunohistochemistry (IHC) testing
How can I learn about my genetic risk for colon cancer?
You can learn about your genetic risk by talking with a genetic counselor. Appointments are made through your local Kaiser Permanente Genetics Department. You can ask your healthcare provider for a referral or call the Genetics department yourself.
What should I expect when I call the Genetics Department?
You may be scheduled for an appointment to review the family history and talk about genetic testing. Before the visit, you are encouraged to watch an online video program called “Inherited Cancer Risks”. The video program covers general information about cancer risk genes and may help you decide if you want a Genetics appointment. It can also help you prepare for an appointment.
How do I prepare for a genetic counseling appointment?
Before your genetic counseling appointment, gather as much medical information as you can about your family. It is helpful to know the type of cancer and the age at diagnosis for anyone who has had cancer. It is also helpful to get a copy of genetic test results from anyone who has had testing.
- Use our Family History Form to help keep track of the information you learn.
- You may be asked to get medical records or death certificates on some of your family members. This can help show whether or not genetic testing is useful for your family
Last reviewed: January 28, 2021
Reviewed by: Kimberly Barr, MS, LCGC