Is the use of preoperative breast MRI predictive of mastectomy?

BACKGROUND Several recent studies have described increasing rates of unilateral and bilateral mastectomy among women with newly diagnosed breast cancer. The use of breast magnetic resonance imaging (MRI) has also risen rapidly, leading to speculation that the high false-positive rate and need for multiple biopsies associated with MRI may contribute to more mastectomies. The objective of this study was to determine whether newly diagnosed patients who underwent preoperative MRI were more likely to undergo mastectomy compared with those who did not have a preoperative MRI. METHODS A retrospective review was performed of all newly diagnosed patients with breast cancer at our academic breast center from 2004 to 2009. RESULTS The proportion of newly diagnosed patients with breast cancer having MRI prior to surgery increased from 6% in 2004 to 73% in 2009. Of 628 patients who underwent diagnostic MRI, 369 (59%) had abnormal results, 257 (41%) had one or more biopsies, and 73 had additional sites of cancer diagnosed. Patients with a malignant biopsy, or those with an abnormal MRI who did not undergo biopsy, had an increased mastectomy rate (P<0.01). However, patients with a normal MRI or a benign biopsy actually had a decreased mastectomy rate (P<0.05). Although there was a trend toward more bilateral mastectomies, the overall mastectomy rate did not change over this time period. CONCLUSIONS Although there is a strong relationship between the result of an MRI and the choice of surgery, the overall effect is not always to increase the mastectomy rate. Some patients who were initially considering mastectomy chose lumpectomy after an MRI.