Usefulness of magnetic resonance in patients with invasive cancer eligible for breast conservation: a comparative study.

Background: The role of magnetic resonance imaging (MRI) in newly detected breast cancer remains controversial. We investigated the impact of preoperative MRI on surgical management of infiltrating breast carcinoma (IBC).
Methods: We reviewed data of 237 patients with IBC who were suitable for breast-conserving surgery (BCS) between 2009 and 2011. Of these patients, 109 underwent preoperative MRI (46%; MRI group) and 128 did not (54%; no-MRI group). We analyzed MRI-triggered changes in surgical plan and compared differences in rates of positive margins and mastectomy.
Results: Tumor size was larger in the MRI group (16.8 mm vs. 13.9 mm; P < .001). MRI changed the initial surgical planning in 18 of 109 patients (16.5%) because of detection of larger tumor diameter requiring wider resection (8 patients [7.3%]) or additional malignant lesions in the ipsilateral (9 patients [8.2%]) or contralateral breast (1 patient [0.9%]). MRI-triggered treatment changes included mastectomy (n = 12), wider excision (n = 5), and contralateral BCS (n = 1). Reoperation rates for positive margins after BCS appeared higher in the no-MRI group (4.1% vs. 8.6%), but the difference missed statistical significance (P = .9). Overall mastectomy rates were higher in the MRI group (13.7% vs. 7.0%; P < .05). The likelihood of having a change of treatment resulting from MRI was significantly higher for patients with tumors > 15 mm and for those with positive lymph nodes.
Conclusion: Lymph node positivity and tumor size > 15 mm may predict an MRI-triggered change in surgical plan. Preoperative MRI resulted in higher mastectomy rates justified by biopsy-proven additional foci of carcinoma and did not significantly reduce reoperation rates for positive margins.
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