Bilateral breast MRI needed even after mastectomy

By Kate Madden Yee, AuntMinnie.com staff writer

May 8, 2020 — Follow-up of breast cancer survivors with breast MRI should be bilateral, even in asymptomatic women who underwent mastectomy, according to a study published May 6 in the American Journal of Roentgenology.

Researchers from the University of California, San Francisco (UCSF) found a breast MRI cancer detection rate of 10 cancers per 1,000 exams on the mastectomy side during the course of contralateral breast MRI cancer screening, wrote a team led by Dr. Molly Chapman.

“The results of our study support current American College of Radiology practice parameters for MRI to perform all breast MRI studies as bilateral examinations, even after mastectomy,” the researchers wrote. “Additionally, the cancer detection rate of 10 cancers per 1,000 examinations in our cohort indicates a need for larger prospective studies on the benefit of MRI screening in this patient population.”

The question of whether it’s appropriate to add imaging surveillance to clinical follow-up in women who have undergone mastectomy has been under debate, and there are no guidelines regarding this imaging application, Chapman’s team noted.

Therefore, the team sought to evaluate breast MRI’s performance in detecting asymptomatic cancer recurrence in the mastectomy bed during examinations performed to screen for cancer in the opposite breast. To do so, Chapman and colleagues reviewed 402 breast MRI exams performed in 191 asymptomatic women who had unilateral therapeutic mastectomy between January 2010 and January 2016.

Most of the breast MRI exams were performed in women who had undergone breast reconstruction after mastectomy (79.4%), and most were benign (98.3%). Seven of the 402 exams, or 1.7%, were categorized as BI-RADS 4, suspicious for malignancy; of these, four were biopsied, and all were cancerous (PPV3, 100%). Of the three that were not, follow-up imaging showed resolution of the initial finding, translating to a positive predictive value of abnormal findings (PPV2) of 57.1%. Two of the MRI exams produced false negatives, for a negative predictive value of 99.5%.

The study results highlight the need to include the mastectomy side in MRI breast cancer recurrence screening, according to the group.

“Although breast MRI is not routinely used to screen the postmastectomy area, women with a history of unilateral therapeutic mastectomy may undergo breast MRI of the contralateral native breast,” the authors wrote. “This population is expected to increase with rising mastectomy rates and because women with a personal history of breast cancer and dense breast tissue or who were younger than 50 years old at cancer diagnosis are now considered candidates for high-risk screening MRI.”