WASHINGTON (AP) _ Surgically removing both breasts before disease strikes lowers the risk of breast cancer to almost zero for a rare group of women who have a combination of gene mutations and family members with the disease, a study found.
The study, appearing Wednesday in the Journal of the National Cancer Institute, involved women who had close female relatives with breast cancer and who had a mutation in one of two genes, BRCA1 or BRCA2, that have been linked to breast cancer.
Researchers said that the average woman has about a 10 percent lifetime risk of breast cancer. For the women in the study, the lifetime risk was 55 percent to 85 percent.
For such women, said Dr. Lynn C. Hartmann of the Mayo Clinic, a double mastectomy may be considered a reasonable option.
``Those of us outside and looking in may feel very different than the women who must confront this issue,'' said Hartmann, the first author of the study.
Most experts said that double mastectomy is not expected to become a major choice of preventive therapy, even for the rare women who are at such exceptional risk.
``It is a valuable observation,'' Dr. Patrick Borgen, a breast surgeon at Memorial Sloan-Kettering Cancer Center in New York, said of the study. ``But nobody has been willing to build the future of breast cancer prevention'' on a procedure that removes both breasts.
In the study, Hartmann and her colleagues analyzed data from 214 high-risk women who had chosen double mastectomies to prevent breast cancer. From this group, the researchers identified 26 who had both a strong family history of breast cancer and a mutation in the BRCA1 or BRCA2 gene.
The researchers found that, at an average of about 13 years after undergoing double mastectomies, none of the 26 women had developed breast cancer.
Without the surgery, the researchers estimated, six to nine of the 26 women would have breast cancer. They translated this result into an estimated breast cancer risk reduction of 89.5 percent to 100 percent.
Hartmann said the study was conducted because even a careful mastectomy does not remove all the cells that can lead to breast cancer in high-risk women.
``The ductal system of the breast does not conform to a defined area,'' she said. ``Ductal cells can exist up near the collarbone or down in the armpit or even on the abdominal wall.''
The concern, said Hartmann, was that if the surgery left behind a nest of these cells, women with gene mutations ``might not be protected at all'' by double mastectomies.
But the new study, she said, shows that ``if a surgeon removes the vast majority of the tissue at risk, then it removes the chance of breast cancer.''
Hartmann said that most women who choose double mastectomies also undergo breast reconstruction.
She said a survey of women who have undergone the procedure found that most were satisfied they had chosen to have their breasts removed because it substantially reduced their high risk of cancer.
Debbie Saslow, head of breast and gynecological cancer care at the American Cancer Society, said the study ``may be a big advance'' for some high-risk women.
Saslow said that most cancer counselors do not recommend double mastectomies, but the procedure is usually mentioned as an option.
``This study will help women who do choose it to be more confident about their decision,'' said Saslow.
Dr. Deborah K. Armstrong, a breast cancer specialist at Johns Hopkins University Medical Center in Baltimore, said the option of a double mastectomy applies ``only to a very select group of people.''
She said only 5 percent to 10 percent of breast cancer patients are in a group identified as ``high risk'' and only about half of this group would have one of the BRCA mutations.
``Only an extremely small percentage of patients will choose this option,'' said Armstrong.
Instead, she said, many choose to take five-year courses of Tamoxifen, a drug that studies suggest can reduce breast cancer risk by about 50 percent.