Few women have an MRI to screen for breast cancer, but they are often used to help diagnose cancer after it has been detected through a mammogram or a physical.
The sensitivity of an MRI helps doctors determine the size and position of the tumor prior to surgery. New evidence suggests this extra preparation may not be necessary.
The study in the journal Lancet finds women undergoing breast cancer surgery fared just as well without MRI exams before the operation .
Despite these findings, some experts caution that MRIs may still be worth the added costs, because they detect a small percentage of cancers that other tests can miss.