For those with a previous breast cancer, are breast MRIs the new standard as a supplement to mammograms, and how often are MRIs recommended?

MRI is a new technology for the breast and I don't feel that we've sorted out the exact use yet. Right now the accepted use of MRI is in the newly diagnosed woman, to check that breast for a second known site of a breast cancer on the same side, and to check the opposite breast for an unknown site of possible cancer. The use of MRI to screen breast cancer survivors is not yet accepted. It is a very expensive tool. It is difficult to interpret; there is a high rate of false positives—seeming abnormalities that show up on the exams and are not real abnormalities—like a false alarm.
At the recent ASCO (American Society of Clinical Oncology) meeting, a very interesting report was presented on the role of MRI scans in women without a personal history of breast cancer but who were known to have a breast cancer gene abnormality. In this study, researchers compared MRI scanning to mammography and ultrasound, and in this high risk population, MRI scans seemed to be able to find small, invasive breast cancers earlier than mammography and ultrasound. Mammography seemed to be better at finding non-invasive (DCIS) breast cancers. There were nearly 2000 women in this study. This information is promising but still early.