Older women with breast cancer could be undergoing unnecessary breast surgery as a result of the growing use of magnetic resonance imaging (MRI) scans, a U.S. study warned Wednesday. Researchers from the Yale University looked at the use of breast MRI and surgical care in 72,461 American women aged 67 to 94 who were diagnosed with breast cancer between 2000 and 2009. During the study period, the researchers found \"a considerable increase\" in the use of preoperative breast MRI. It was used in 1 percent of the patients in 2000, and 25 percent in 2009. The researchers also found that women who received an MRI were more likely to subsequently undergo more aggressive surgical treatment. In women who received mastectomy, 12.5 percent of those who had MRI received bilateral mastectomy, while only 4.1 percent of those who did not have MRI had bilateral mastectomy. Women undergoing MRI were also more likely to have a procedure called contralateral prophylactic mastectomy, in which both breasts are surgically removed when cancer is only found in one breast. Among women who underwent mastectomy, 6.9 percent of women who had an MRI underwent contralateral prophylactic mastectomy, compared to 1.8 percent in women who did not have an MRI. The researchers said that these data \"are concerning\" because the long-term benefits associated with bilateral mastectomy for older women with breast cancer are unclear. \"There has been no randomized controlled clinical trial demonstrating improved outcomes for women who undergo preoperative breast MRI at any age,\" said Brigid Killelea, assistant professor of surgery at the Yale School of Medicine and first author of the study. \"Breast conserving therapy, when feasible, remains the preferred approach for women with early stage breast cancer,\" Killelea added.