The selective use of preoperative magnetic resonance imaging (MRI) did not reduce the number of reoperations among women with breast cancer, a recent study has indicated. Furthermore, MRI overestimated the extent of disease in a considerable number of women.

The retrospective cohort study focused on women with operable breast cancer who had undergone treatment with a single surgeon from January 2006 through December 2010. The main outcome measures were reoperation rate and pathologically avoidable mastectomy at initial operation.

Of the 313 women studied, 120 had undergone preoperative MRI. These patients were more likely than the women not receiving preoperative MRI to have dense or very dense breasts (68.4% vs 22.3%), to be younger (mean age 53.6 years vs 59.5 years), and to be of non-Hispanic white race/ethnicity (61.7% vs 52.3%). The type of surgery performed (mastectomy vs partial mastectomy) was similar between the two groups, as was the incidence of lobular carcinoma (8.3% in the MRI group compared with 5.2% in the non-MRI group). Although the mean pathological size of the index tumor among the women in the MRI group was larger than that in the other group (2.02 cm vs 1.72 cm), the extent of disease was comparable: 75.8% of the MRI women and 82.9% of the non-MRI women had pathologically localized disease.

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As the researchers reported in Archives of Surgery (2012;147[9]:834-839), the reoperation rate was similar between the two groups, at 19.1% for the women undergoing preoperative MRI compared with 17.6% for the non-MRI group. The similarities held even when the cases were stratified by breast density, tumor size, or lobular carcinoma histologic findings.

Pathologically avoidable mastectomy (multifocal or multicentric MRI and unifocal histopathologic findings) was observed in 12 of 47 women (25.5%) who underwent preoperative MRI imaging and mastectomy.