Clinical ScienceLocoregional treatment of breast cancer in women with and without preoperative magnetic resonance imaging

•Preoperative MRI in women stage 0-III breast cancer does not increase mastectomy.•There was a greater use of radiation therapy in older women with MRI undergoing BCS.•Results mitigate concerns about unnecessary MRI-associated mastectomies.

BackgroundPreoperative magnetic resonance imaging (MRI) use has increased among older women diagnosed with breast cancer. MRI detects additional malignancy, but its impact on locoregional surgery and radiation treatment remains unclear.MethodsWe examined the associations of preoperative MRI with initial locoregional treatment type (mastectomy, breast conserving surgery [BCS] with radiation therapy [RT], and BCS without RT) and BCS reoperation rates for Surveillance, Epidemiology, and End Results Medicare women diagnosed with stages 0 to III breast cancer from 2005 to 2009 (n = 55,997).ResultsWe found no association of initial locoregional treatment of mastectomy (odds ratios [OR], 1.04; 95% confidence intervals, .98 to 1.11) or reoperation after initial BCS (OR, .96; 95% confidence intervals, .89 to 1.03) between women with preoperative MRI (16.2%) compared to women without MRI. However, women with MRI who had initial BCS were more likely to undergo RT (OR, 1.09 [1.02 to 1.16]).ConclusionsPreoperative breast MRI in Medicare-enrolled women with stages 0 to III breast cancer was not associated with increased mastectomy. However, in older women with MRI undergoing BCS, there was a greater use of RT.