Hereditary colon cancer
Jennifer Siettmann, MS, GC, is a cancer genetic counselor on staff at Banner Good Samaritan Medical Center. Her office can be reached at (602) 839-6385.
Question: Multiple family members have had colon cancer and I’m concerned about getting it too? Is there a genetic link and how can I find out if I’m at risk?
Answer: There are inherited genetic predispositions for colon cancer and many other types of cancer, which makes them hereditary cancers.
About five to 10 percent of all cancers are hereditary and caused by a genetic change or mutation that increases a person’s likelihood of getting cancer. These mutations are passed on in an autosomal dominant manner, meaning there is a 50 percent chance a person will pass on the mutation to his or her offspring.
Common traits of hereditary cancers include diagnosis at an early age (younger than 50), presence of the cancer in two or more generations, two or more close relatives with the disease, multiple new tumors, and cancer in paired organs such as the colon and uterus.
Two predispositions for hereditary colon cancer are Lynch syndrome, also known as hereditary nonpolyposis colorectal cancer (HNPCC), and familial adenomatous polyposis (FAP).
Lynch syndrome is caused by a genetic mutation and generally presents with an early diagnosis of colon or rectal cancer, usually around age 45, as well as the presence of cancer outside the colon, such as uterine, ovarian, stomach, small bowel and brain cancers. Those with Lynch syndrome have up to an 82 percent chance of developing colon or rectal cancer, and they should have a colonoscopy every one to two years starting between age 20 to 25.
FAP is a less common but equally dangerous predisposition for hereditary colon cancer that causes the formation of hundreds to even thousands of cancer-causing colon polyps. Colonoscopy is the recommended screening approach.
Genetic testing helps identify mutations in specific cancer genes and determine whether there is a genetic predisposition for cancer. It also can help guide a person’s individual cancer screening and treatment recommendations.
While not everyone wants to know their risk of cancer, genetic counseling can be an important tool for understanding familial connections for those who do want to know. Genetic counselors assist in documenting family history, providing a personal risk assessment, explaining hereditary cancers, and conducting testing if desired and appropriate.
The National Cancer Institute website (http://www.cancer.gov/) is a great resource for information about hereditary cancers and genetic testing. Be sure to speak with your physician about your family history of cancer to determine whether genetic counseling is right for you.