The breast cancer gene
May 26, 1999
Web posted at: 10:06 AM EDT (1406 GMT)
By Stephanie Slon
What if you knew from childhood that later in life you were going to be stricken with a deadly disease? With the discovery of two gene mutations that dramatically increase breast cancer risk, many women face this potential reality.
Two genes for breast cancer
The genes BRCA1 and BRCA2 control the development of two protein compounds that researchers believe suppress the growth of tumors. These genes interfere with this protective action, diminishing the body's ability to defend itself against the overgrowth of cancerous cells. The BRCA genes are dominant, meaning that if one of your parents carries the gene, you have a 50-50 chance of inheriting it.
Between 50 and 85 percent of women with the BRCA genes will develop breast cancer by age 70, compared with the one in nine lifetime risk that the average American woman faces. BRCA-related cancer patients also tend to have a lower survival rate than those with other forms of the disease.
Although the occurrence of the breast cancer gene is relatively rare in the general population, it has a much higher prevalence among people of Ashkenazi (Eastern European or Russian) Jewish heritage. Approximately 2.5 percent of this ethnic group carries the genetic defect.
Scientists have yet to sort out how this inherited tendency toward disease interacts with environmental factors such as diet, weight and exposure to toxins. Only 5 to 10 percent of all breast cancers can be traced to BRCA1 or BRCA2. What's more, BRCA genes do not always show up in breast cancer cases where a strong family history suggests genetic involvement. These facts lead some scientists to suspect that there is a BRCA3, a BRCA4 and even a BRCA5 gene waiting to be discovered.
Testing for the genes
In the meantime, the issue of testing for BRCA1 and BRCA2 remains controversial. Having the gene is not a clear indicator that cancer will inevitably follow, so a woman who goes forward with the test should be prepared for the ambiguity of the results.
Another drawback is that genetic testing costs in the range of $2,000 - a charge often not covered by health insurance. Before testing, a woman should also consider if she wants this information to be part of her medical record. A positive result may be a red flag to insurance carriers, leading to coverage problems in the future. Because of the complexity of these issues, genetic counseling is highly recommended for anyone considering the test.
Those who fit the criteria for BRCA testing include any Ashkenazi Jewish woman with a relative who has had breast or ovarian cancer, as well as anyone with two or more relatives with breast or ovarian cancer or any family history of these cancers before age 50. Women who already have breast cancer can be tested to help clarify other family members' risk.
Beating the odds
Even though there is no clearly defined prevention strategy for women who test positive for BRCA1 or BRCA2, women with the gene can take action to protect themselves against cancer.
The first step is making lifestyle changes to avoid possible risks such as smoking, high-fat diet, excess alcohol consumption and hormonal drugs, including birth control pills and estrogen replacement therapy. Another option for women who carry the breast cancer gene is to undergo earlier and more frequent mammograms and breast exams than would otherwise be recommended.
However, there is no hard evidence that these stepped-up screening efforts increase their chances against cancer. Yet there is hope that breast cancer prevention drugs such as tamoxifen will prove effective against BRCA-related cancers.
A radical choice
Finally, some women make the radical decision to have their breasts surgically removed before cancer can invade. This move can have mixed results. Ninety percent of the time, women who undergo this surgery remain cancer-free, but at a cost. A 1998 study in the Journal of Clinical Oncology showed that the increase in life expectancy was often undercut by an overall loss in quality of life after the surgery.
The bottom line is that breast cancer is a disease for which there is often no cure and no definitive prevention strategy. Certainly insights into the genetic underpinnings of the disease hint at the promise of a future medical breakthrough. But until that time, awareness of the BRCA gene is a mixed blessing for many women.
Copyright 1999 by WebMD, Inc. All rights reserved.
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