Cancers occur more frequently in some families than expected. This is often the case with malignant melanoma and with cancers of the breast, colon, ovary, endometrium, in which about 10 percent of cases are caused by a defective gene that is passed from one generation to the next.
A comprehensive family history often identifies persons and families at risk. Family histories suggestive of hereditary predisposition include the following:
- When several close relatives have cancers such as malignant melanoma or tumors of the breast, colon or ovaries. Members of these families may have one type of these cancers or a combination of these cancers
- When cancer affects several siblings or when there are multiple cases of a cancer across generations
- When there is a history of developing malignancy 15 to 20 years earlier than it ordinarily occurs.
- When individuals have more than one type of cancer; for example, a diagnosis of breast cancer at age 35 and ovarian cancer at age 55
If you think you have a hereditary risk for developing cancer, you should seek a health-care provider who has training and expertise in explaining and ordering genetic tests. On the first visit with a genetics health-care provider you should expect a thorough family history to be taken and a family tree to be drawn. Often this makes it easier to see a hereditary link in a family.
The health-care provider should discuss the family history and the your personal risks for developing cancer(s) and interpret these risks to the family. For some families, the possibility of genetic susceptibility is high, and then options for genetic testing are offered. For many families, genetic testing will clarify whether they have a genetic predisposition to develop cancer and what organs might be at risk.
Once individuals and families are identified as possibly having a genetic predisposition to developing malignancy, steps may be taken to reduce risk and develop a program of screening to detect cancer early, when treatment is most effective. Family members may also benefit from taking direct steps to reduce that risk for developing cancer by changing their lifestyle (such as diet, exercise, etc.) and by taking chemoprevention agents (such as Tamoxifen to prevent breast cancer). For those individuals with a known mutation, even more aggressive prevention measures may be recommended, such as prophylactic surgery.
Intensive education and counseling are the most effective ways to help these individuals and families to understand their risk for developing a particular cancer and how to reduce that risk and detect cancers early. It usually takes several sessions lasting an hour or more to really understand what happens during genetic testing and get enough information for patients to make a good decision about testing.
Testing is now commercially available for genetic changes associated with hereditary risk for breast and ovarian cancer, as well as some colorectal cancers and melanoma. Those individuals who test positive for one of these defective genes have a greater than 90 percent chance of developing one of these malignancies. Testing for other hereditary cancer syndromes will undoubtedly become available in the near future. It is a very personal decision and often emotionally difficult for families.
The benefits of testing may include relief for those who test negative and the ability to make good choices about cancer prevention including preventive surgery (such as a prophylactic mastectomy to prevent breast cancer) and how to best detect the cancer early. Individuals also need to understand the risks associated with genetic testing, including psychological distress upon learning there is a very high risk of developing cancer, loss of privacy, job discrimination and insurance discrimination. If testing is chosen individuals will need counseling after testing to understand the results and provide further recommendations and emotional support.
All of these services are available to members of the community through the Saint Louis University Cancer Center. Thanks to funding from the Missouri Foundation for Health and the St. Louis affiliate of the Susan G. Komen Foundation, education and counseling services are provided free of cost by Suzanne Mahon, R.N., DNSc, AOCN, APNG. For those who are uninsured, underinsured or lack the financial resources to pay for genetic testing, financial assistance is available. For more information, please contact Dr. Mahon at (314) 577-8854.