Breast Cancer Screening with MRI in Women with Over 20% Lifetime Risk

Introduction: To reduce mortality, magnetic resonance imaging (MRI)-screening from age 25 years is advised to women with high breast cancer (BC) risk due to a BRCA1/2 pathologic variant. Recently, two randomized studies investigated whether MRI-screening can reduce mortality more for women with moderate BC risk than mammography (Mm) and the associated cost-effectiveness. Methods: The FaMRIsc trial randomized women aged 30–60 with 20–45% lifetime risk based on family history between screening with annual MRI and Mm every other year (MRI-group) or annual Mm (Mm-group). The DENSE trial randomized women from the general population aged 50–75 with negative results on their screening mammogram and extremely dense breast tissue between additional MRI-screening or no additional screening (control group). Results: In the FaMRIsc MRI-group (n = 674) compared to the Mm-group (n = 680), invasive cancers were smaller (median size 9 vs. 17 mm, p = 0.01) and less often node positive (N+ 17% vs. 63%, p = 0.023). In incident rounds, significantly fewer large or node-positive cancers were detected with MRI (N+ 2/18 vs. 5/8, p < 0.01), suggesting mortality reduction and less need for adjuvant chemotherapy. The false-positive rate remained higher with MRI, especially at high density. In the Dense study, MRI detected 79 extra cancers with a median size of 9.5 mm. After 2 years follow-up, there were in the MRI-group (n = 4783) significantly fewer interval cancers compared to the Mm only group (n = 32, 312): 0.8/1000 screens vs. 5/1000 respectively (p < 0.001). By MISCAN modeling, screening women at familial risk with only MRI every 18 months from 35–60 years followed by screening in the national program till age 75 was estimated to reduce mortality 8% more than yearly mammography, at acceptable cost for Europe. This could be achieved for women with dense breasts by MRI-screening once every 4 years from 50–75 years. Conclusion: Screening with only MRI can in women with an estimated lifetime breast cancer risk ≥20% reduce mortality more than mammography in every degree of breast density cost-effectively and likewise in women age 50–75 years with high breast density.