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| Screening, Genetic Tests, and Counseling |
Early diagnosis of cancer greatly increases survival; therefore, regular exams for cancer can help to prevent deaths from cancer. These include mammograms and Pap tests for women, prostate cancer tests for men, colonoscopy exams for colon cancer, and regular physical exams for other types of cancer. Individuals with a strong family history of cancer should consider genetic tests for cancer and cancer risk counseling. The focus of cancer risk counseling is the individual's personal risk of developing cancer and appropriate actions based on that risk.
The discovery of the BRCA1 and BRCA2 genes associated with early development of breast cancer has allowed women with a family history of early breast cancer to be tested for mutations in these genes. Only five to ten percent of breast cancers show evidence of inheritance. Of these, forty-five percent are associated with a mutation in BRCA1 and thirty-five percent with BRCA2. The gene or genes for the remaining twenty percent are not yet known. If the BRCA1 and BRCA2 test results are negative, there is no evidence that the woman will have breast cancer because of these mutations. However, she may get breast cancer because of somatic mutations in these or other genes. If the BRCA1 or BRCA2 test is positive, other family members may be tested to determine whether the gene was inherited. If other family members are negative, then there is less chance of hereditary risk of this form of cancer, although the individual with the mutation does carry an increased risk of the disease. If the test is positive in other family members, there is an increased hereditary risk for breast cancer in that family. The absence of hereditary risk does not mean that there is no other risk for breast cancer.
Decisions based on genetic tests can be very complicated. Individuals must be fully informed about the risks before they can make reasonable decisions. Genetic counselors are trained to help individuals make difficult decisions based on genetic tests. The cumulative risk of breast cancer to age seventy for a woman with a BRCA1 mutation is about fifty-seven to eighty-five percent depending on whether she is in a high-risk family. Some women find the fear of cancer so disruptive to their lives that they choose mastectomy to prevent cancer. (This is called prophylactic mastectomy.) Similarly, women with BRCA1 have a high lifetime risk of ovarian cancer, causing some of them to choose to have their ovaries removed. While these are difficult decisions, the availability of genetic information provides individuals with information that they can use to make such important medical decisions. A young woman with a strong family history of ovarian cancer might find by genetic testing that she does not have the BRCA1 mutation and should not consider removal of her ovaries.