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Broader Gene Tests for Breast, Ovarian Cancer Might Benefit Some: Study
Women who don't have BRCA mutations could have other high-risk genes that affect treatment choices
By Dennis Thompson
THURSDAY, Aug. 13, 2015 (HealthDay News) -- Some women with a family history of breast or ovarian cancer might benefit from a broader genetic test that includes more than 20 genes that have been found to increase cancer risk, a new study suggests.
Genetic tests have tended to focus solely on BRCA1 and BRCA2, the two genetic mutations that have been proven to dramatically increase a woman's risk for breast or ovarian cancer, the researchers said.
But women who don't carry BRCA1 or BRCA2 could still have another genetic mutation that is the source of a history of cancer in their families, explained study senior author Dr. Leif Ellisen, program director of the Center for Breast Cancer at Massachusetts General Hospital and a professor at Harvard Medical School, both in Boston.
Ellisen's research concluded that a broad genetic test could help doctors better advise and treat about half of the women who have a genetic predisposition to cancer that's not due to either BRCA1 or BRCA2.
"In the majority of women in which these other mutations were found -- 52 percent of the group -- you would actually make a different recommendation than you would based on personal and family history alone," Ellisen said.
The study was published online Aug. 13 in the journal JAMA Oncology.
A recent and dramatic drop in the cost of genetic testing has sparked an ongoing debate about the positives and negatives of such testing, said Dr. Len Lichtenfeld, deputy chief medical officer for the American Cancer Society.
For example, a company called Color Genomics now offers a 19-gene test to help women gauge their risk of breast and ovarian cancer for only $249, he said. The company will even help women find a doctor who will order the test on their behalf.
But Ellisen said that such testing, done indiscriminately and without proper counseling, could promote a lot of fear and even prompt some women to undergo unneeded mastectomies or ovary removals.
"It has to be communicated in an accurate way," he said. "If a woman comes in and she's had a cancer scare, and you tell her she has this significant cancer risk gene, she might be tempted to go out and have one of these surgeries when the risk isn't that high and it really isn't warranted."
To see whether a broad-panel genetic test would be helpful in some situations, Ellisen and his colleagues recruited 1,046 women who had a family history of breast or ovarian cancer but did not have BRCA1 or BRCA2 mutations.
These women underwent genetic testing using either a 25-gene panel or a 29-gene panel, both of which are commercially available.
The researchers found that 3.8 percent of the women -- 63 total -- carried another type of genetic mutation that would increase their cancer risk, Ellisen said.
In half those cases, the mutation likely would alter the outcome of a cancer risk assessment on the women, researchers concluded. Doctors might recommend additional cancer screening, or even removal of the breasts or ovaries, based on the new genetic info.
"The question was, these people who have a family history, is their risk already high enough that you would have been watching them very closely anyway, and finding this new gene wouldn't have made any difference?" Ellisen said.
"We found that if you do a risk calculation that doesn't include the information about the gene and you make a recommendation, but then you find the gene and you redo the risk calculation, the risk is much different and you would make a much different recommendation," he said.
The researchers also concluded that close female relatives of 72 percent of patients with a cancer-causing mutation would be urged to undergo genetic testing, to see if they carry the same mutation.
But this new data could lead to more confusion than clarity, as the ability to test a person's genetics outpaces the knowledge of how specific genes contribute to cancer, according to Lichtenfeld and Dr. Stephanie Bernik, chief of surgical oncology at Lenox Hill Hospital in New York City.
A ton of research has been conducted on BRCA1 and BRCA2, and the way they affect cancer risk is well documented. They account for about 20 percent to 25 percent of hereditary breast cancers, and about 5 percent to 10 percent of all breast cancers, according to the U.S. National Cancer Institute. They also account for about 15 percent of ovarian cancers.
But not much is known about the cancer risk posed by all these other genes, the cancer experts said. And doctors without proper training in genetics might find it hard to provide quality information for patients.
"We say information is power, and I think it is for many patients, but we don't always know what to do with the information," Bernik said. "With these other genes, the risk is often low to intermediate. If the risk is lower, at what point does the risk become enough to tell a woman that prophylactic surgery is the best route?"
Lichtenfeld agreed, adding that, "in practical terms, the question is, are we ready for this in the everyday practice of medicine?"
Ellisen believes that only women with a family history of breast or ovarian cancer should undergo genetic testing at this time. He added that the genetic testing must be combined with the woman's personal and family history to produce a nuanced assessment of her cancer risk.
"If that information is conveyed inappropriately to patients, they may think they have something bad when really they don't have anything bad at all," he said.
Once more is known about all of these genes, there may come a day when genetic testing becomes a broad standard of care for all people, starting with a test conducted on newborns, Lichtenfeld said.
"We're certainly not there yet," he said. "All of this is a learning process, and we're still very much in that mode of finding out what all of this really means."
Visit the U.S. National Cancer Institute for more on genetic tests for cancer risk.
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