Hypothesis The use of preoperative magnetic resonance (MR) imaging may have an effect on the reoperation rate in women with operable breast cancer.
Design Retrospective cohort study.
Setting University medical center.
Patients Women with operable breast cancer treated by a single surgeon between January 1, 2006, and December 31, 2010.
Intervention Selective preoperative MR imaging based on breast density and histologic findings.
Main Outcome Measures Reoperation rate and pathologically avoidable mastectomy at initial operation.
Results Of 313 patients in the study, 120 underwent preoperative MR imaging. Patients undergoing MR imaging were younger (mean age, 53.6 vs 59.5 years; P < .001), were more often of non-Hispanic white race/ethnicity (61.7% vs 52.3%, P < .05), and more likely had heterogeneously dense or very dense breasts (68.4% vs 22.3%, P < .001). The incidence of lobular carcinoma (8.3% in the MR imaging group vs 5.2% in the no MR imaging group, P = .27) and the type of surgery performed (mastectomy vs partial mastectomy, P = .67) were similar in both groups. The mean pathological size of the index tumor in the MR imaging group was larger than that in the no MR imaging group (2.02 vs 1.72 cm, P = .009), but the extent of disease was comparable (75.8% in the MR imaging group vs 82.9% in the no MR imaging group had pathologically localized disease, P = .26). The reoperation rate was similar between the 2 groups (19.1% in the MR imaging group vs 17.6% in the no MR imaging group, P = .91) even when stratified by breast density (P = .76), pT2 tumor size (P = .35), or lobular carcinoma histologic findings (P = .26). Pathologically avoidable mastectomy (multifocal or multicentric MR imaging and unifocal histopathological findings) was observed in 12 of 47 patients (25.5%) with preoperative MR imaging who underwent mastectomy.
Conclusion The selective use of preoperative MR imaging to decrease reoperation in women with breast cancer is not supported by these data. In a considerable number of patients, MR imaging overestimates the extent of disease.