Utility of breast MRI for evaluation of residual disease following excisional biopsy

Background: Because benign postoperative changes may overlap those of malignancy, the utility of breast MRI following an excisional biopsy is unclear. We sought to investigate the ability of MRI to predict residual disease following an excisional biopsy for breast cancer. Materials and Methods: We reviewed 93 patients who underwent surgical treatment for stage 0-III breast cancer at our institution from January 2005 to May 2008. All patients had previously undergone excisional biopsy with subsequent MRI. Patient, tumor, and treatment characteristics were collected. Descriptive statistics were utilized for data summary and data were compared using Fisher's exact or χ² tests. Results: The mean age of the 84 patients who had additional surgery following MRI was 51 ± 7 y. Thirteen (15%) patients had only postoperative changes on MRI; six had residual disease on final pathology. Of 71 patients with MRI findings suspicious for residual disease, 54 (76%) had pathologic confirmation, while 17 (24%) had only benign pathology. The sensitivity and specificity of MRI following excisional biopsy were 90% and 29%, respectively. Overall, 49 (58%) of the 84 patients underwent mastectomy, including 11 of 24 (46%) with negative final pathology. Patient age, tumor size, tumor grade, biomarker profile, nodal status, and MRI findings were not predictive of surgical treatment type (P > 0.05). Conclusion: Although excisional biopsy decreases the specificity of breast MRI, its sensitivity remains high. Nearly 50% of patients with a suspicious MRI and negative final pathology underwent mastectomy, suggesting that additional biopsy of all suspicious MRI findings is necessary to avoid surgical overtreatment.