The Effects of Adding Preoperative Magnetic Resonance Imaging to Patients with Invasive Cancer Eligible for Breast Conserving Surgery: A Comparative Study

Introduction: Magnetic resonance imaging (MRI) have been widely used in evaluation of patients with newly detected breast cancer, however its role in preoperative planning remains controversial. We investigated whether pre-operative (MRI) influence surgical planning, rates of positive margins, and mastectomy rates, when added to preoperative work-up of patients with infiltrating carcinoma (IBC) eligible for breast conserving surgery (BCS). Methods: This is a retrospective analysis on 237 patients with IBC suitable for BCS on the basis of standard triple assessment (i.e. physical exam, mammography and ultrasonosgraphy) and treated during the period January 2009-June 2011. Of those, 109 underwent preoperative MRI (46%, MRI-group) and 128 did not (54%, no-MRI group). Variations in surgical treatment due to MRI were evaluated, and both rates of re-operations for initial positive margins and mastectomy rates compared in the two study groups. Results: Demographic data, histopathological characteristics, and tumor stage were similar. Tumor size was bigger in the MRI-group (16.8 mm vs. 13.9 mm, p<0.001). MRI changed the initial surgical planning in 18/109 patients (16.5%). Reasons for change in treatment plan included detection of larger tumor diameter requiring wider resection (8 cases, 7.3%) or finding of additional malignant lesions in either ipsilateral (9 cases, 8.2%) or contralateral breast (1 case, 0.9%). MRI-triggered treatment changes were mastectomy (N=12), wider excision (N=5) and contralateral BCS (N=1). Rates of re-excision for positive margins after primary BCS attempt appeared higher in the no-MRI group (4.1% vs 8.6%) but the difference missed statistical significance (p=0.9). Overall mastectomy rates were higher in the MRI-group (13.7% vs 7.0%, p<0.05). Conclusions: In our experience preoperative MRI altered the original treatment plan in more than 16% of patients. MRI was associated with higher mastectomy rates justified by detection of additional foci of carcinoma, but did not significantly reduce the re-excision rates for positive margins.