Clear guidelines about the utilization of magnetic resonance imaging (MRI) in breast cancer detection and management are needed, according to Constance Lehman, MD, PhD, of the Seattle Cancer Care Alliance. It is being overutilized among women for whom it offers few benefits (and potential harms), but it is underused in appropriate situations, she said at the 33rd Annual Miami Breast Cancer Conference, held March 10–13 in Miami Beach, Florida.
Overuse of breast MRI leads to unnecessary mastectomies among women who could instead undergo breast conserving surgery or systemic therapy with radiation, she said.
“I can’t stress enough how important I think it is for breast MRI to be done only in selected patient populations,” she said. “Unfortunately, that’s not how breast MRI is being used. We found that 75% of all screening MRIs performed were in women with less than a 20% lifetime risk—whereas in women at greater than 20% lifetime risk, less than 1.5%—almost none—had received an MRI.”
Standards are needed that can offer better guidance on the appropriate use of breast MRI for women at high risk of breast cancer and to “dissuade those ‘worried-well’ women who are at low risk,” Dr. Lehman said.
Breast MRI is not recommended for the routine evaluation of patients with “challenging breast exam or difficult mammogram,” she said, but is recommended for patients with axillary adenopathy, or unknown primary tumors, among whom 60% of women harbor a primary breast tumor.
“In patients with a current breast cancer diagnosis, MRI provides a more accurate assessment of extent of disease and [involvement] of the contralateral breast,” Dr. Lehman noted.
For patients at high risk of breast cancer, screening MRI offers “acceptably low rates of false positives,” but for lower-risk women, MRI can lead to overinterpretation and overtreatment, she warned. “The goal of breast MRI in the era of precision medicine is to reduce mastectomies.”
And that means eschewing routine clinical use of breast MRI among low-risk women, she believes.
“The quality of the MRI exam really matters, and the timing matters,” she advised. Parenchymal enhancement varies in images acquired in pre-contrast, intermediate, and delayed post-contrast phases, for example, and existing tumors can be missed in late-phase images. Breast enhancement on MRI can “balloon” when patients cease tamoxifen treatment, she noted, and pregnancy and lactation can affect follow-up MRI findings.
“Innumerable studies around the world show that we can find cancer in high-risk women using MRI,” she was quick to add. “There is no question that MRI is the most sensitive modality for detecting cancer. Many people still prefer screening ultrasound but that’s not consistent with the literature; repeated rounds of screening ultrasound adds detection of only about 3 additional cancers per 1,000 cancers, vs adding another 15 cancers per 1,000 with MRI.”
That has led to an ongoing reconsideration of MRI’s potential role for intermediate-risk patients. “The jury’s still out on that,” Dr. Lehman said.