Standardized pretreatment breast MRI--accuracy and influence on mastectomy decisions.

BACKGROUND AND OBJECTIVES: Routine pretreatment breast magnetic resonance imaging in newly diagnosed cancer patients remains controversial. We assess MRI accuracy and influence on mastectomy decisions after institution of standardized pretreatment MRI.
METHODS: A prospectively collected database of 74 consecutive new invasive breast cancer patients with pretreatment breast MRI was reviewed for treatment choice, radiologic, and pathologic results. Thirty-eight of 72 patients with available surgical records underwent mastectomy. Mastectomy preoperative and operative electronic records were reviewed for treatment decision analysis.
RESULTS: Seventeen of 72 (23.6%) invasive breast cancer patients were likely influenced to undergo mastectomy by new information from MRI. MRI reported that the multifocal/multicentric (MF/MC) rate was 20 of 72 (27.8%) versus 19 of 72 (26.4%) by surgical pathology. MRI sensitivity for MF/MC disease was 89.5% versus 11.8% for mammography. MRI specificity was 84.2%. All three false positives declined recommended preoperative biopsies. MRI MF/MC diagnosis highly correlated with pathology results, P < 0.001.
CONCLUSIONS: Increased mastectomy rate from 29 to 52.8% after standardization of pre-treatment breast MRI for invasive cancer is largely due to MRI findings of increased extent of disease. These MRI findings correlate well with pathologic findings and appear to justify the performance of mastectomies in these patients.