Although their tumors are confined to only one breast, more women are asking doctors to remove their healthy, unaffected breast as well to reduce their risk of finding another tumor later.

Authors of a new study say they may have found a way to help some of these women avoid unnecessary mastectomies, although other experts say the decision remains as difficult as ever.

Though tumors don't tend to spread from one breast to the other, women with cancer in one breast do have a higher risk of developing another, unrelated tumor in the opposite breast, says Kelly Hunt of M.D. Anderson Cancer Center, author of a study released today in Cancer, which tracked women from 2000 to 2007 Those additional tumors may be too small to detect when a woman's first cancer is diagnosed, making a preventive mastectomy a "rational" choice for some women, she says.

In Hunt's study, 25 of 542 women who opted for preventive mastectomies had cancer in the opposite breast. Her analysis shows that three factors increased the risk:

• If a woman had more than one tumor in the original breast.

• If her original tumor started in the milk-producing lobes but spread like seeds around the breast instead of forming one solid lump.

• If she had a high risk according to a scale called the "Gail model," which considers factors such as age, race, the age of the patient when she had her first child and the family history of breast cancer.

Hunt hopes her findings will help more of her patients stop worrying or questioning their decisions.

Other experts say the study may not help at all. It could even scare additional women into unnecessary surgery, says the University of Washington's Julie Gralow.
More cancer patients having healthy breasts removed

Very few of the women with such risk factors actually had cancer in the opposite breast, and doctors don't need to remove the second breast to protect women, Gralow says. She notes that doctors can often find these hidden tumors through the use of MRI.

Mastectomies aren't the only way to prevent a new cancer, says Eric Winer, a breast cancer specialist at Boston's Dana-Farber Cancer Institute. Women also can reduce their risk with hormones or chemotherapy.