Breast Magnetic Resonance Imaging in the Management of Early Breast Cancer: Implications for Partial Breast Irradiation
Two oncology research groups (NSABP & RTOG) are conducting a study of accelerated partial breast irradiation (APBI), which involves targeting only the tumor bed after lumpectomy for radiation treatment. This differs from standard therapy, which involves treating the entire breast plus additional dose ("boost") to the tumor bed. To be eligible for this study, it is important that the patient have no other areas of cancer in the breast, as these areas would go untreated with APBI. To screen for this, breast MRI is done. This review was done to see the rates of detection of other areas of cancer, which were otherwise not detected (also called "occult disease").
Radiologists experienced in evaluating breast MRI read the tests. Participants were women who were to participate in the APBI study, which included tumor size <3cm, Tis-T2, N0-N1 and negative margins). Of the 260 patients (ages 28-86 years), MRI identified concerning lesions in 36 women. These lesions were in the same breast as the current cancer. Another 16 women were found to have lesions in the opposite breast. These women had ultrasounds, which resulted in 27 biopsies, 16 of which led to diagnoses of cancer (12 in the same breast, 4 in the opposite breast). The risk of finding a second cancer was highest in women with known invasive lobular cancer (18%), as opposed to invasive ductal cancer (3%). Age and menopausal status did not significantly affect rates of detection.
This study demonstrates a 5.8% detection rate for occult second cancers in patients with early-stage breast cancer identified by MRI. The presence of second sites of malignancy would certainly be expected to increase local recurrence rates and potentially death from breast cancer if left untreated. Based on these results, MRI appears to be a tool that should be utilized to further identify patients who are not optimal candidates for APBI.
Partially funded by an unrestricted educational grant from Bristol-Myers Squibb.