Removing the healthy breasts of women with genetic mutations that often trigger breast cancer can save their lives, Dutch researchers found in the strongest study yet to show that the controversial strategy works.
In the study, none of the women who chose to undergo preventive, or prophylactic, mastectomies developed the often-deadly cancer. In a comparison group of women who also had the mutant genes and opted only for regular checkups, one-eighth got breast cancer and one woman died.
Scientists had questioned whether the extreme approach really prevents breast cancer because some breast tissue remains after surgery and the dangerous mutant genes are in every cell in the body.
``We can say to our patients that this method of prevention is nearly 100 percent effective and that they can sleep without fear of getting breast cancer,'' said Dr. Jan Klijn, chairman of the Rotterdam Family Cancer Clinic, part of Erasmus University Medical Center, where the research was done.
Other experts, however, cautioned that the women, many in their 20s and 30s, were followed for only three years on average.
``My guess is that some small number of women might'' later develop breast cancer despite the mastectomy, said Dr. Marvin Schwalb, director of the Center for Human and Molecular Genetics at the University of Medicine and Dentistry of New Jersey.
The research was reported in Thursday's New England Journal of Medicine.
From 1992 on, Klijn and colleagues studied 139 women after they were determined by DNA testing to have a dangerous mutation on either of the breast cancer susceptibility genes, BRCA1 and BRCA2. The mutations carry a lifetime breast cancer risk of up to 85 percent.
More than half of the women _ 76 _ chose to have a prophylactic mastectomy, with most later having breast reconstruction.
The 63 other women chose regular follow-up: annual mammograms or MRI screenings, examination by a doctor every six months and monthly breast self-exams. Eight developed breast cancer during the study, with half detecting it themselves between screenings.
``It's a really fine study,'' said Dr. Lynn Hartmann, a cancer specialist at the Mayo Clinic in Rochester, Minn. ``Three or four years ago, women were doing this with no proof at all that it worked.''
Hartmann and colleagues reported in 1999 that prophylactic mastectomies cut the risk of developing breast cancer at least 90 percent.
They reviewed medical records of 639 women who underwent the procedure from 1960 through 1993. But such retrospective studies are valued less by researchers than prospective ones, where each patient group gets exactly the same care.
The women in the Mayo Clinic study sought prophylactic mastectomies because they had relatives with breast cancer and feared getting it. DNA testing for the mutant genes was not possible at the time.
Subsequent testing found 16 of them had the mutant genes, but none have developed breast cancer in 12 years of follow-up, Hartmann said.
In an editorial in the journal, Dr. Barbara L. Weber of the University of Pennsylvania and Dr. Andrea Eisen of McMaster University in Canada said that the studies by Klijn and Hartmann suggest that prophylactic mastectomy, while extreme, is the most effective prevention strategy.
They urged support for research to find better breast cancer screening methods and medications that can prevent the disease.