Objective: The purpose of our study was to assess the diagnostic performance of breast MRI in evaluating residual disease in patients after excisional biopsy for breast cancer on the basis of both morphologic and kinetic features.
Materials and methods: Of 5304 breast MRI examinations performed between January 2007 and December 2011, 308 evaluated postoperative sites after excisional biopsy of breast cancer. Among these, 203 patients who were not treated with chemotherapy or radiotherapy before MRI and underwent definitive surgery within 30 days after MRI were enrolled. MRI findings were analyzed on the basis of contrast-enhanced subtraction images. The enhancement patterns were classified into four categories: no enhancement (P1), thin regular rim enhancement (P2), thick or irregular rim enhancement (P3), and nodular or nonmasslike enhancement (P4) around the postoperative sites. The enhancement kinetics were assessed as follows: persistent, plateau, and washout pattern.
Results: From 207 breast MRI examinations in 203 patients, 144 breasts had residual breast cancer at histopathologic examination after definitive surgery. When P1 and P2 were considered negative for residual cancer and P3 and P4 were considered positive, the sensitivity, specificity, positive and negative predictive values, and accuracy were 79.9%, 73.0%, 87.1%, 61.3%, and 77.8%, respectively. The specificity and positive predictive value improved to 90.5% and 91.7%, when analyzed with washout enhancement kinetics as another positive finding for residual cancer. A statistically significant trend of decreasing specificity and positive predictive value (p < 0.05) was found with the passage of a time interval between excision and breast MRI.
Conclusion: Although the overlapping features of the postsurgical changes and malignant lesions remain as the limitations, dynamic contrast-enhanced breast MRI is a useful tool for residual disease prediction after excisional biopsy for breast cancer. Combined use of morphologic and kinetic evaluation parameters improved the diagnostic performance. We do not recommend that MRI be unreasonably delayed after excisional biopsy considering the risk of prolonging definitive surgery.