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Wednesday, 21 November 2007

Genetics and breast cancer

Nearly 200,000 American women are diagnosed with breast cancer each year, and between 5 percent to 10 percent of them have a heritable form of the disease. Geneticists have identified mutations on the BRCA1 and BRCA2 genes that predispose a person to develop breast cancer. Women with alterations on these genes have up to an 85% greater lifetime chance of developing breast cancer than women with unaffected genes. The mutations are also associated with an increased risk of ovarian cancer. People of Ashkenazi Jewish descent have a higher incidence of inheriting these mutations than those in other ethnic groups. Although breast cancer in men is far less common, a mutated BRCA2 gene, in particular, increases their possibility of having the disease. Furthermore, people with altered BRCA1 and BRCA2 genes have a slightly greater risk to develop cancer of the pancreas, stomach, or prostate than people without the mutations.
Genetic testing for the mutated BRCA1 or BRCA2 genes should be considered by those who have had ovarian cancer at any age or breast cancer before they were 50 or have relatives meeting the same parameters; people with family histories of two or more cases of breast and/or ovarian cancer; and males with breast cancer. The preferred procedure is to first test a family member who has had breast or ovarian cancer. If this is not possible, then an at-risk family member can be tested directly.
A positive result indicates that the patient is at higher risk for cancer. However, it cannot tell whether cancer will actually occur, or when, or how aggressively. That is why it is important to review test results with an experienced genetic counselor. Some of the options that can be considered in discussion with a genetic counselor include:
Careful monitoring: Increased frequency of mammograms and clinical breast exams can help catch breast cancer at an earlier and more treatable stage. Most importantly, is to begin screening at-risk persons at an earlier age than is recommended for the population at large.
For ovarian cancer, monitoring through transvaginal ultrasound, CA-125 blood tests, and clinical exams can sometimes find cancer at an early stage, but it is not clear if these methods can reduce the risk of death from ovarian cancer.
Prophyltactic Surgery: Removal of the breasts (mastectomy), ovaries and fallopian tubes (salpingo-oophorectomy), or both the breasts and the ovaries can reduce (but not eliminate) the risks of developing breast or ovarian cancer. A Salpingo- oophorectomy may be recommended for women past childbearing age, as ovarian cancer is difficult to detect in its early stages. The younger the patient with altered genes is when she has a preventive mastectomy, the greater the potential benefit. Surgery is a particularly complex and highly personal option to consider and is best made by the patient with information by her physician and her genetic counselor and the support of her family.
Chemoprevention: In general, tamoxifen has been found to be effective in reducing the risk of developing cancer and in reducing the chance that cancer will reoccur in women at increased risk for developing the disease.

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