Breast cancer gene testing may be appropriate for more young breast cancer patients.
Women who have breast cancer before age 50 and who have few female relatives on one side of their family tree should be considered candidates for genetic testing for cancer genes, say a team of researchers at City of Hope. Their research challenges the accuracy of some breast cancer prediction models that do not take family structure into account. Their findings appear in the June 20 issue of the Journal of the American Medical Association.
Most physicians agree that genetic testing for genes linked to breast cancer, including mutated BRCA genes, is not recommended for the general population without cancer, since the risk of carrying such a gene is low - about one in 800. Predictive models that are currently used to estimate the likelihood of a breast cancer gene mutation to determine who should receive genetic testing rely on family histories. Some testing guidelines suggest genetic testing in women with at least two or more first-degree or second-degree relatives with related cancers. However, opinions differ over recommending testing for women with no family history of breast or ovarian cancer who develop breast cancer at an early age.
The researchers, led by Jeffrey Weitzel, M.D., director of the Department of Clinical Cancer Genetics at City of Hope, have found that women who had early breast cancer and no first-degree or second-degree female relative who lived past age 45 on either their mother or father's side, were more likely to be BRCA carriers.
"Genetic testing may be a valuable tool for women with early onset breast cancer to determine if a BRCA mutation contributed to their cancer," Weitzel said. "Armed with that knowledge, they can take steps to prevent second occurrences of breast cancer or ovarian cancer."
The study included 1,543 women seen at the City of Hope Cancer Screening & Prevention Program Network high-risk clinics for genetic cancer risk assessment and BRCA gene testing between April 1997 and February 2007. Three hundred six of these women had breast cancer before age 50 years and no first- or second-degree relatives with breast or ovarian cancers.
In 153 cases (50 percent), the patients did not have enough older female relatives to indicate there may be a breast cancer gene trait in their families. BRCA gene mutations were detected in 13.7 percent of participants with limited versus 5.2 percent in women with a family tree that is sufficient to determine cancer risk. Participants with few female relatives who lived past 45 on one side of their family had a three-fold greater likelihood of being found to be carriers of a BRCA gene mutation than those with adequate family structure.
"The fact that commonly used models for estimating BRCA gene mutation probability were insensitive to family structure as a predictive factor is a cautionary note for community practitioners," the researchers wrote.
Mutations in the BRCA genes have been linked to increased risk of breast, ovarian and fallopian tubal cancer in women and possibly prostate cancer in men. Women with mutations in the BRCA1 or BRCA2 genes who do not take preventive measures have up to a 40 percent risk of having breast cancer develop in the opposite breast within 10 years of the first cancer, researchers have found.
Genetic testing helps women determine their relative risk of cancer so they can consider preventive measures such as taking estrogen-suppressing medicines (like tamoxifen), having a preventive mastectomy or having their ovaries removed before cancer develops. Women with cancer-linked BRCA mutations can also take steps to increase monitoring for breast cancer, such as more frequent mammograms using more sensitive technology such as breast magnetic resonance imaging, the City of Hope researchers say.
Weitzel says he hopes the results of the study will change the understanding of who should receive genetic testing, especially in primary care physicians who may not ask about relatives with cancer beyond two generations.
The research was supported by grants from the National Institutes of Health and the California Cancer Research Program of the University of California.
About City of Hope
City of Hope is a leading research and treatment center for cancer, diabetes and other life-threatening diseases. Designated as a Comprehensive Cancer Center, the highest honor bestowed by the National Cancer Institute, and a founding member of the National Comprehensive Cancer Network, City of Hope's research and treatment protocols impact care throughout the nation. Founded in 1913, City of Hope is a pioneer in the fields of bone marrow transplantation and genetics, and shares its scientific knowledge with medical centers locally and globally, helping patients battling serious diseases. For more information, visit http://www.cityofhope.org.
Source: Medical News Today
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