Breast MR Imaging before Surgery: Outcomes in Patients with Invasive Lobular Carcinoma by Using Propensity Score Matching.

Purpose To investigate the association between preoperative breast magnetic resonance (MR) imaging and surgical outcomes in patients with invasive lobular carcinoma (ILC) by using propensity score matching to decide whether MR examination is beneficial in the ILC subtype of breast cancer. Materials and Methods The authors identified 603 patients with ILC who underwent surgery between January 2005 and December 2016. Of the 603 patients, 369 (61.2%) underwent MR imaging. The authors calculated the MR detection rate of additional lesions that were occult at mammography and ultrasonography and analyzed any alterations in surgical management. After propensity score matching, 196 pairs of patients were allocated to the groups, and the 17 possible confounding variables regarding patient and tumor characteristics and various clinical features were well balanced between the patients who underwent MR imaging and those who did not. Surgical outcomes were compared. Results Of the 369 patients who underwent MR imaging, additional lesions were detected in 145 (39.3%); 95 of the 145 patients (65.5%) had malignant lesions. A change in surgical management occurred because of MR findings in 94 of the 369 patients (25.5%). According to pathologic findings, this change was appropriate for 84 of the 94 patients (89.4%). In the propensity score-matched analysis, breast MR imaging was associated with lower odds of repeat surgery (odds ratio, 0.140; P < .001) and similar likelihood of initial mastectomy (odds ratio, 0.876; P = .528) and final mastectomy (odds ratio, 0.744; P = .151) compared with patients without breast MR imaging. Conclusion Preoperative MR imaging is useful for detecting additional synchronous malignancy and significantly reducing the likelihood of repeat surgery without increasing the rate of mastectomy in patients with ILC. RSNA, 2018.