MRI Screening Reduces Interval Breast Cancer in Women with Dense Breasts
■ Major Focus: Determining outcomes of adding supplemental breast MRI to screening in women with extremely dense breasts.
■ Key Result: Supplemental breast MRI screening significantly reduced interval cancers as compared with mammography alone in this study cohort.
■ Impact: Decreased interval cancers with screening breast MRI provides an essential first step for showing a benefit to overall breast cancer mortality.
Dense breast tissue limits detection of breast cancer by mammography and increases risk and aggressive features of breast cancer. While supplemental imaging with MRI or US increases detection of breast cancers in women with extremely dense breast tissue, effects of added imaging on health outcomes remain unknown. Bakker et al report a multicenter, prospective clinical trial conducted by investigators in the Netherlands, where women ages 50–75 undergo digital screening mammography every 2 years. Investigators randomized women with the highest breast density (quantified by Volpara imaging software), classified as category D in the latest BI-RADS criteria, to receive an invitation to an additional screening MRI plus follow-up mammography in 2 years versus follow-up mammography alone. The study reported 2.5 versus 5.0 interval cancers per 1000 screenings for MRI-invitation and mammography-only groups, respectively. A total of 59% of women in the MRI-invitation group underwent supplemental MRI screening with 16.5 cancers detected per 1000 screenings in these women. Results showed 17.4% and 26.3% positive predictive values for recall and biopsy with MRI screening. Cancers detected with MRI exhibited more differentiated, hormone receptor–positive tumors at histology, suggesting MRI screening identified less-aggressive, slower-growing breast cancers. Supplemental MRI screening produced 79.8 false-positive diagnoses per 1000 screenings. As noted by the authors, showing a decrease in interval cancers between biennial screening mammograms represents an essential prerequisite to establishing that supplemental MRI screening would reduce mortality in women with extremely dense breasts, although a much larger study with longer follow-up would be required to define a benefit to survival. Benefits of supplemental screening MRI for women with extremely dense breasts may be less in systems with annual screening mammography. While these results are promising, the widespread implementation of MRI screening in women with extremely dense breasts will require technical advances to reduce imaging time, cost of MRI, and consequences of false-positive diagnoses.
Bakker MF, de Lange SV, Pijnappel RM, et al. Supplemental MRI screening for women with extremely dense breast tissue. N Eng J Med 2019; 381:2091–2102. doi: 10.1056/NEJMoa1903986