Bilateral breast MR imaging: is it superior to conventional methods for the detection of contralateral breast cancer?

Background: Breast MR imaging has emerged as a highly sensitive modality for the imaging of breast tumors. However, there have been no reports concerning the usefulness of bilateral breast MRI to evaluate the contralateral breast in Japan. The purpose of this study was to examine the frequency of primary bilateral breast cancer, and to investigate the role of bilateral breast MRI in the detection of contralateral breast cancer.
Methods: A retrospective review was performed of 556 consecutive women who had undergone surgery for the primary breast cancer. MR imaging was performed on a 1.5-T system. Both the breasts were examined in the coronal plane on the first-, second-, and fourth-phase dynamic images, acquired at 30, 90 s, and 4.5 min, respectively. The affected single breast was sagittally examined on images obtained in the third phase at 3 min.
Results: Twenty-four (4.3%) patients had bilateral breast cancer, 14 (2.5%) had synchronous cancer and 10 patients (1.8%) had metachronous cancer. In the 14 cases with synchronous cancer, bilateral breast malignancy was suspected at the time of the initial diagnosis in 6 cases. The detection rate of 18 contralateral breast cancer cases by only MMG, only US, MMG and US, and MRI were 50% (9/18), 67% (12/18), 78% (14/18) and 100% (17/17), respectively. For 8 of these cases with a second synchronous cancer, the corresponding rates were 75, 88, 100 and 100%, respectively. For the 10 cases with a second metachronous cancer, the rates were 30, 50, 60 and 100%, respectively.
Conclusion: Bilateral breast MRI is a more sensitive for the detection of contralateral breast cancers compared with conventional imaging methods. In particular, bilateral MRI also allows detection of metachronous contralateral cancers at an earlier stage during the postoperative follow-up period.