Breast cancer allayed by mastectomy.

Preventive mastectomies protect against breast cancer in many women with a high inherited risk of getting the disease, a 33-year study shows.

A study of 214 women at high risk of breast cancer who had undergone preventive mastectomies at the Mayo Clinic in Rochester, Minn., showed that only three women--1.4 percent--subsequently developed breast cancer. Two died. The operations were performed between 1960 and 1993.

Among 403 sisters of members of this group who didn't undergo mastectomy, 156--nearly 39 percent--had breast cancer at some point. Of these patients, 90 died from the cancer. The study was published in the Jan. 14 NEW ENGLAND JOURNAL OF MEDICINE.

The researchers evaluated a woman's risk of breast cancer by looking at the incidence of breast and ovarian malignancies among her close and distant relatives.

The study provides data that women at risk can use to make a decision about surgery, says study coauthor Lynn C. Hartmann, a medical oncologist at Mayo. "It's my sense as a clinician that high-risk women are quite well informed and may have already made a decision [about surgery] before I see them," she says. However, "at first, women tend to overestimate their risk."

Traditional preventive mastectomy, called subcutaneous mastectomy, removes breast tissue but retains the nipples. Mayo surgeons used that technique in all the surgeries in the study. An alternative today, called total mastectomy, couples removal of more breast tissue with better breast reconstruction, Hartmann says. "Most people would do a total mastectomy today, if they were going this direction," she says.

Women in at-risk families now have genetic testing with which to ascertain their risk, she adds, an advantage most of the women in this test didn't have.