New Test Shows Promise as Quick Way to Identify Women with Genetic Breast and Ovarian Cancer Risk (dateline October 27, 2000)
Researchers have finished a preliminary study of a fast, inexpensive test to determine which women may have a genetic predisposition to breast or ovarian cancer. The test analyzes cells taken from the inside of a womans cheek (the buccal cells) to determine whether she is carrying mutations of BRCA1 (breast cancer gene 1) or BRCA2 (breast cancer gene 2). Genetic mutations account for approximately 5% to 10% of breast and ovarian cancer cases. While larger studies of the cheek swab test are still needed before it becomes more common, the researchers say the preliminary results show great potential as an inexpensive genetic screening tool.
In the study, researchers tested the check cell samples of 16 women at high risk of breast and ovarian cancer due to family history. The women also underwent standard genetic testing. Standard genetic testing of BRCA gene mutations requires drawing and analyzing blood samples. The cheek swab test was able to accurately detect BRCA gene mutations in all 11 women who tested positive for the mutations with standard testing, although the new test did detect one mutation that did not exist.
While Gabriel Cohn, MD of Baystate Medical Center and his colleagues said that the cheek swab test must be tried on 1500 additional women to confirm the results, the researchers said the results of the preliminary test "show great promise as an inexpensive screen for BRCA mutations."
Standard BRCA gene testing involves DNA sequencing and costs approximately $2,700 in the United States. This high cost prevents it from becoming more commonly used to identify women at high risk of breast and ovarian cancer. However, the new cheek swab test simply checks for a shorter protein in the BRCA genes (which signals a defect). According to the researchers, this new method significantly reduces the cost of the test. Only the women who test positive for BRCA mutations with the cheek swab test would need to have standard DNA sequencing to confirm the results.
BRCA1 and BRCA2 are two tumor suppressor genes that, when functioning normally, help repair damage to DNA (a process that also prevents tumor development). In 1994, researchers discovered that women who carry mutations of BRCA1 or BRCA2 are at higher risk of developing both breast and ovarian cancer than women who do not have these genetic mutations. Sandhya Pruthi, MD, a breast health specialist at the Mayo Clinic, estimates that 20% of women who carry BRCA1 mutations will develop breast cancer by age 40, 51% by age 50, and 87% by age 60.
There are over 200 known genetic mutations associated with BRCA1 and BRCA2 genes. Women who test positive for BRCA defects will not necessarily develop breast cancer; but they are at a higher risk for the disease than women without these gene mutations. Thus, these women may wish to take precautionary measures to reduce their chances of developing breast cancer. These measures may include more frequent screening, using the drug tamoxifen, or considering prophylactic mastectomy (preventive breast removal).
While genetic testing can help identify women at high risk of breast or ovarian cancer, it is a controversial topic among health care providers and women. There are advantages and disadvantages to knowing BRCA test results. While knowing about BRCA mutations may help women take preventive measures to help guard against cancer (such as adherence to recommended screening guidelines), the results may also cause stress and panic among some women. Click here to learn more about issues to consider before undergoing BRCA gene testing.
Guidelines for the early detection of breast cancer:
- All women between 20 and 39 years of age should practice monthly breast self-exams and have a physician performed clinical breast exam at least every three years.
- All women 40 years of age and older should have annual screening mammograms, practice monthly breast self-exams, and have yearly clinical breast exams.
- Women with a family history of breast cancer or those who test positive for the BRCA1 or BRCA2 mutations may want to talk to their physicians about beginning annual screening mammograms earlier than age 40, as early as age 25 in some cases.
- The medical study, "Immunoassay Predicts BRCA1 and BRCA2 Mutations in Buccal Cells," was presented by Gabriel M. Cohn, MD at the American Society of Human Genetics meeting in Philadelphia in October 2000. An abstract of the study is available at http://www.faseb.org/cgi-bin/ashg00/show?127851
- To learn more about BRCA gene mutations and other genetic risk factors for breast cancer, please visit http://www.imaginis.com/breasthealth/genetic_risks.asp
- To learn more about candidates for genetic testing, please visit http://www.imaginis.com/breasthealth/brca.asp
- To learn more about ovarian cancer, please visit http://www.imaginis.com/ovarian-cancer/