Effect of preoperative MRI on mastectomy and contralateral prophylactic mastectomy rates at a community hospital by a single surgeon.

Magnetic resonance imaging (MRI) use in the preoperative evaluation of newly diagnosed breast cancer (BC) patients is rising. We evaluated MRI as a function of surgical year with respect to mastectomy and contralateral prophylactic mastectomy (CPM) rates by a single surgeon. From January 2000 to December 2010, 1,279 patients with 1,296 breast cancers were identified. Our breast MRI was installed in April 2006. Mastectomy and CPM rates were evaluated by surgical year and stratified as "pre-MRI" or "MRI" depending on whether surgery occurred before or after April 2006. There was a significant increase in the percentage of patients undergoing MRI in the "pre-MRI" versus "MRI" era (17.2% versus 78.7%, p < 0.001). In contrast, mastectomy rates decreased with 29.9% undergoing mastectomy before 2006 versus 24.5% after 2006 (p = 0.038). Except for 2007, where CPM rates dropped to 7.1%, CPM rates increased from 16.7% in 2000 to 51.9% in 2010 (p = 0.033). The use of MRI, additional MRI findings and additional MRI biopsies were not associated with the decision for CPM. Age <50 was the only factor associated with CPM (RR = 2.12, p = 0.001). In our community hospital, mastectomy rates have decreased despite the increased use of preoperative MRI. MRI alone may not explain the increasing rates of mastectomy reported in other series. CPM rates have dramatically increased over time, seemingly independent of MRI use. Prospective studies are needed to assess the role of surgeon bias, along with other factors, in surgical decision making.