Colon Cancer
What is the chance for colon cancer?
Anyone can get colon cancer. It is the third most common cancer diagnosis. The lifetime risk for colon cancer is about 1 in 20, or about 5%.
Can colon cancer be inherited?
Cancer is not inherited, but in some families a predisposition to cancer may be inherited. Colon cancer is due to mutations (errors) in genes that control the growth of cells in the colon. Most mutations happen randomly over a lifetime and are not inherited. Only about 5% of people with colon cancer have an inherited risk for cancer due to a specific gene mutation.
Hereditary Colon Cancer: Should you have genetic testing?
What is known about the genetic conditions that predispose to colon cancer?
There are two genetic conditions that account for most inherited colon cancer predisposition:
Lynch syndrome (previously called HNPCC or hereditary non-polyposis colon cancer)
Lynch syndrome is a condition caused by an error (mutation) in any one of several different genes. Individuals who have a mutation in one of the Lynch syndrome genes have a higher risk for colon cancer and other cancers. In families that carry such a gene mutation, there are often several adults with colon cancer in more than one generation. Women in these families may have cancer of the uterus (endometrium) or ovary as well. There are also a number of other cancers that are more likely to happen in families with Lynch syndrome: stomach, urothelial (kidney/urinary tract), brain, small intestine, pancreatic.
For more information: Lynch syndrome
Familial Adenomatous Polyposis (FAP)
FAP is caused by a mutation in a gene responsible for controlling cell growth. This condition accounts for only about 1% of colon cancers. Individuals who have FAP develop many polyps (usually 100's) and, without surgery, will eventually develop colon cancer. This condition needs close follow-up starting in childhood. Anyone with a close relative (parent, brother, sister or child) with a large number of colon polyps should call the Genetics department for consultation. The hallmark of this condition is multiple polyps (usually 100's or more) in the colon. This condition is often first noted in the teens or 20's.
For more information: Familial Adenomatous Polyposis (FAP) syndrome
How do you identify someone who might have a gene mutation that predisposes to colon cancer?
We identify those at a higher genetic risk by reviewing the family history and tumor testing.
Family History: A review of the family takes into account the ages of the family members, when they were diagnosed with cancer, the particular types of cancer, and the relationship between family members who have cancer. We consider both the mother's and the father's sides of the family, since these genes can be carried by men as well as women. Here are some findings that increase the chance for an inherited risk for cancer:
Cancer that happens earlier than usual
Individuals with more than one type of cancer
Many relatives with similar cancers
Use our Family History Form to gather information about cancer in your family.
Tumor Testing: Tests done directly on cells from a tumor can also help find individuals who are more likely to have an inherited risk for cancer.
Colorectal Cancer: Immunohistochemistry (IHC) testing
How can I learn more about my personal risks for carrying a mutation in a gene that predisposes to colon cancer?
Evaluation and counseling about your family history of colon cancer is available through your local Genetics department. You may be referred by your healthcare provider, or you may call your closest Kaiser Permanente Genetics Departmnet yourself.
What should I expect if I call my Genetics Department to inquire about my colon cancer risk?
Individual counseling may be scheduled to obtain an evaluation of your risk for carrying a predisposing gene mutation for colon cancer. DNA testing to detect these mutations is available for selected families only. Information about a personal inherited risk is available regardless of whether testing is offered or desired. For those who do have testing, at least two counseling appointments will be scheduled. The evaluation/counseling/testing process often takes weeks or months to complete.
How can I prepare before contacting the Genetics Department?
Before contacting Genetics, it is helpful if you have gathered all the medical information you can about your family members. It is especially important to know the type of cancer and the age of diagnosis for affected individuals. We are interested in all cancers in the family, so that we may have the most information possible. We will take a complete family history, including family members without cancer. Medical records/death certificates may be requested to help determine your risk before genetic testing is offered.
Genetic information often has an impact on many individuals within a family, and may be emotionally complicated by the nature of the relationships within a family. These issues will be considered and discussed during the process of genetic counseling.