SAN DIEGO The increasingly common practice of surgically removingboth breasts while they are still healthy is an effective, ifradical, way of preventing breast cancer in women at high risk of thedisease, a study finds.
Until recently, bilateral prophylactic mastectomy, as doctorscall it, was rare. But the development of genetic screening testsfor breast cancer has increased demand for this approach.
When a woman discovers she has a high genetic susceptibility tocancer, there is little she can do besides frequent checkups or haveher breasts removed. Some doctors are reluctant to offer the geneticscreening test because of uncertainty about whether a preemptivemastectomy actually works.To help settle the issue, doctors from the Mayo Clinic followedup on 950 women who have had bilateral prophylactic mastectomiesbecause of a family history of breast cancer. They found that itreduced their breast cancer risk by 91 percent.It was not, however, totally effective. Even when the breastsare cut off, surgeons often leave behind tiny bits of breast tissueon the chest wall. These remnants can still turn cancerous.Furthermore, undetected cancer may have already spread to other partsof the body before the breasts are removed.The study, directed by Dr. Lynn C. Hartmann, followed women whohad the surgery between 1960 and 1993 - before screening for breastcancer genes became common over the past two years.Hartmann said her findings are the first to suggest thatmastectomies in women with cancer genes will work as intended."It's an extreme approach," she said. "For a woman who decidesto proceed, at least she now has some clear information instead of aquestion mark."Hartmann presented her results Sunday at a conference sponsoredby the American Association for Cancer Research.While there are no clear figures on how many women are optingfor mastectomies to prevent cancer, Dr. Henry T. Lynch of CreightonUniversity said the numbers have clearly increased since thediscovery of two powerful cancer genes in 1994 and 1995.Mutant forms of these genes, called BRCA1 and BRCA2, togethercause about 5 percent to 10 percent of all breast cancer and 5percent of all ovarian cancers. While rare, they greatly increasethe cancer risk for those who get them.A woman with either BRCA1 or BRCA2 has about an 85 percentlifetime risk of breast cancer. BRCA1 also gives her a 40 percent to60 percent risk of ovarian cancer, while BRCA2 causes a 10 percent to20 percent risk of ovarian cancer. They also cause less dramaticincreases in the risk of colon cancer and prostate cancer in men.The genes are suspected in women whose families include manypeople with breast or ovarian cancer, often at unusually young ages.In the Mayo Clinic study, two-thirds of the women had theirbreasts removed because of their family histories of the disease,while the rest were concerned by frequent biopsies that producedworrisome findings.The women's average age when they had the surgery was 43, andthey have been followed for an average of 17 years. Based on theirrisk factors, the doctors would have expected 76 cases of breastcancer by now. Instead, seven have occurred.Lynch said his own followup shows that three-quarters of womenwho find they have the cancer genes say preemptive removal of theirovaries is a reasonable choice, while one-quarter say they willconsider breast removal.
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