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From Chapter 24: Selected Medical Practices, Problems, and Procedures
GENETIC TESTING AND INHERITED RISK
All breast cancer appears to be associated with alterations in specific genes in one or more breast cells, but research indicates that only 5 to 10% of breast cancer is inherited in the sense that it runs in families. In other words, 90 to 95% of all breast cancer is not inherited. So far, researchers have identified several genes, most notably BRCA1 and BRCA2, which they think are associated with breast cancer. Everyone is born with these genes, receiving a copy of each from her father and mother. If a woman receives an abnormal or mutated copy from either parent, her risk of developing breast cancer may be increased. If she has a BRCA1 or BRCA2 mutation and is from a family with a strong history of breast and/or ovarian cancer (several family members on one side of the family with breast and/or ovarian cancer in several generations, particularly in women under 40; cases of bilateral breast cancer; and/or cases of male breast cancer), her risk of developing breast cancer in her lifetime may be about 70%. At present, there is no accurate estimate of the risk for a woman with one of these mutations who does not have a strong family history of breast or ovarian cancer.
Researchers have developed blood tests that can identify BRCA1 and BRCA2 mutations. Initially, these tests were administered primarily within research protocols; now they are commercially available and are aggressively marketed by the biotech companies that developed them. This is problematic for several reasons. Genetic testing should be considered only in certain limited situations. A positive test result does not mean that the individual will develop breast cancer; it means only that if she has a strong family history and a family member with cancer who has had a positive test result for the same mutation, she has a greatly increased risk of developing breast cancer. Without this family history, her risk is unknown. A negative test does not mean a woman will never develop breast cancer; it means that she has the same lifetime risk as most other women in the U.S.
The measures you can take if your test result is positive are quite limited at this time. Some physicians recommend frequent mammography beginning at age 25, or 10 years earlier than the youngest age at which a family member has developed the disease. One problem with this strategy is that mammography is much less effective in younger women because of the density of their breast tissue, and there is no evidence that it will detect breast cancer at an early stage. There are also unanswered questions about the safety of exposing young women who are at high risk of developing breast cancer to repeated X rays.
Another possible strategy is prophylactic -- that is, preventive -- surgery. This is a drastic step that is reassuring to some women from high-risk families, but its effectiveness is still unproved (see box on p. 613).
Genetic testing can cause great psychological distress and create a variety of problems for individuals and their families. Anyone considering genetic testing needs to get in-depth counseling from a trained genetic counselor. Research centers that conduct tests under a research protocol are more likely to have doctors and other professionals who are experienced in guiding individuals and their families through this complicated process. However, genetic testing is now available through private physicians. Some doctors may suggest it too casually and inappropriately, for example, to assist in a decision about whether or not to prescribe birth control pills or hormone therapy. Far too little is known about the meaning of these genetic tests for physicians to use them as a basis for this type of medical decision. (See also the boxed text on genetic testing in chapter 25, The Politics of Women's Health and Medical Care.)
Undergoing genetic testing may put an individual and her family at risk for discrimination. As of late 1997, only half the states in the U.S. had enacted laws that provided protection against different forms of genetic discrimination. At that time, federal law had only just been introduced in the Congress to protect people from discrimination in insurance, employment, and other areas on the basis of genetic information or the results of genetic tests. Not only the individuals who have been tested but their family members may be denied health or other types of insurance. The results of a genetic test could be used against an individual in a custody dispute, to deny an adoption, to disqualify someone for organ transplant surgery, or in other ways. Current state and federal laws do not adequately protect the confidentiality of individuals who undergo genetic testing; there are numerous ways in which such information could be inadvertently or deliberately disclosed. All genetic testing should be accompanied by complete information, professional counseling, and comprehensive written informed consent.
It is likely that more genes associated with breast cancer and other diseases will be identified. If and when truly effective treatment and prevention methods are developed for women with inherited gene mutations, genetic testing may have more to offer these women. What it has to offer right now is limited and problematic, and the disadvantages far surpass the advantages for most women.
Copyright © 1984, 1992, 1998 by the Boston Women's Health Book Collective