One reason for the increase, he said, was that more women are getting MRIs, which pick up many "spots" in the breast, most of which mean nothing.
But the study leaves many questions unanswered, Willey said.
"It doesn't tell you what the motivating force was," she said. "Were physicians recommending this, or were patients choosing it? Were some of these prophylactic mastectomies done for symmetry purposes? Was it anxiety, fear?"
The U.S. National Cancer Institute has more on preventive mastectomy.
SOURCES: Stephen B. Edge, M.D., professor, surgery and oncology, and director, Breast Center, Roswell Park Cancer Institute, Buffalo, N.Y.; Jay Brooks, M.D., chairman, hematology/oncology, Ochsner Health System, Baton Rouge, La.; Shawna Willey, M.D., chief, division of breast surgery, and director, Betty Lou Ourisman Breast Health Center, Lombardi Comprehensive Cancer Center, Georgetown University Hospital, Washington, D.C.; Sept. 28, 2009, Cancer