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"With the recent revelation that Angelina Jolie tested positive for the BRCA gene, many patients have been asking questions regarding genetic testing," said Dr. Stephanie Bernik, chief of surgical oncology at Lenox Hill Hospital in New York City. "The general public wants to know what a positive or negative test really means."
Until now, it's been thought that women in families with BRCA mutations who themselves test negative for the gene would have the same risk for breast cancer as women in the general population.
The researchers analyzed data from more than 800 families in England with BRCA mutations. They found that 49 women in those families who tested negative for the family-specific BRCA mutation later went on to develop breast cancer.
Dr. Gareth Evans is an honorary professor of medical genetics and cancer epidemiology at the University of Manchester, in England. "We found that women who test negative for family-specific BRCA2 mutations [still] have more than four times the risk for developing breast cancer than the general population," Evans said in a journal news release.
"We also found that any increased risk for breast cancer is largely limited to BRCA2 families with strong family history and other genetic factors," he said. "It is likely that these women inherit genetic factors other than BRCA-related genes that increase their breast cancer risk."
Evans said about 77 genetic mutations are currently known to be linked with breast cancer risk. Researchers need to identify additional mutations in order to understand why some BRCA-negative women from families with BRCA mutations still have a higher risk for breast cancer, he said.
Bernik said genetic tests may not tell the whole story when it comes to cancer risk.
"Although the risk of getting cancer is not as high [for women who test negative for BRCA2] as that of a gene carrier, it appears to be elevated," she said. "The numbers in this study were not large enough to prove this definitively, but certainly it raises the issue that more attention needs to be given to every family member in genetically susceptible lineages."
Dr. Elisa Port, chief of breast surgery at the Dubin Breast Center, part of the Mount Sinai Health System in New York City, said getting reliable results from a gene test is key to good care.
"Providing patients with accurate information on their risk for developing breast cancer in the future is critical for decision making regarding different options and interventions," Port said. These measures include preventive mastectomy, the option Jolie chose, or taking the anti-breast cancer drug tamoxifen.
The new study suggests that women "who test BRCA-negative are not completely off the hook regarding a higher risk of developing breast cancer," said Port, who is also an associate professor of surgery at the Icahn School of Medicine at Mount Sinai. "More information like this will hopefully help us refine our treatment and recommendations for the individual patient."
-- Robert Preidt
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