Some families have multiple relatives who have colon cancer or other types of cancer. These cancers may be caused by a rare inherited genetic condition called Lynch syndrome, also known as hereditary nonpolyposis colorectal cancer (HNPCC). Lynch syndrome significantly increases your chance of developing colon cancer, and often earlier than the general population — before the age of 45. Nearly 3 percent of all colon cancers are caused by Lynch syndrome. It may also increase your risk of other cancers, such as endometrial and ovarian cancer in women.
The good news is that genetic screening and testing, available at major medical centers, detects Lynch syndrome in an estimated 95 percent of people. The UCSF Cancer Genetics and Prevention Program at Mount Zion, the largest and most comprehensive genetic testing center for cancer in Northern California, has screened over 3,000 people for Lynch syndrome and tested 300 for the syndrome.
If you are thinking about being tested, it is important that you first talk with a professional genetic counselor. The counselor will explain the procedure, its benefits and risks, your test results and help you decide on prevention and treatment options if necessary. They will also counsel you on how to share this information with other family members who may be at risk.
By determining whether you and your family members have Lynch syndrome, you can take steps to seek appropriate medical care and surveillance, such as regular and consistent colonoscopies and check-ups at earlier ages. This can help to detect and prevent cancer, and ultimately, to save lives.
People with Lynch syndrome may have:
Those with Lynch syndrome have a 70 percent chance of developing colon cancer by age 70. Colon cancer patients with Lynch syndrome have an estimated 40 percent risk of developing a second primary colon cancer within seven years of being diagnosed after the first tumor. Women with Lynch syndrome have a 40 percent to 60 percent estimated lifetime risk of developing endometrial cancer.
If you have a family history of cancer, it is extremely important that you let your doctor know. Your doctor will then take a thorough recording of your family history, paying particular attention to cancer diagnoses. If your doctor suspects that you may have Lynch syndrome, they will refer you to a health care professional who specializes in genetic cancer screening, testing and counseling.
In addition, all newly diagnosed colorectal cancer or endometrial cancer patients also should be screened or tested for Lynch syndrome.
Genetic testing involves a simple blood test. Your blood sample is sent to a special laboratory where it is analyzed for certain changes or mutations that indicate Lynch syndrome.
Based on your family history, genetic testing results and other cancer risk factors, your counselors and doctors will provide you with an individualized risk management program that includes recommendations for cancer screening, prevention and treatment options.
If you tested positive for Lynch syndrome, but do not have a cancer diagnosis, or your doctor suspects that you have Lynch syndrome, the following cancer screening plan may be recommended.
Colonoscopy every one to two years, starting at the age of 20 to 25 years (age 30 years in families with a certain mutation known as MSH6) or 10 years younger than the youngest age at diagnosis in the family, whichever comes first.
Reviewed by health care specialists at UCSF Medical Center.
Cancer Genetics and Prevention Program at Mount Zion
1600 Divisadero St., Second Floor
San Francisco, CA 94143-1714
Phone: (415) 885-7779
Fax: (415) 885-3787