A subset of participants* in both arms undergo contrast-enhanced breast MRI within 4 weeks after completion of the 2-year screening US and mammogram. Participants with "probably benign" findings seen only on MRI may undergo an additional breast MRI at the 6-month follow-up visit. Participants with additional suspicious lesions seen only on MRI undergo second-look targeted US for biopsy guidance or MRI-guided vacuum-assisted biopsy after completion of any biopsies or additional views prompted by the 2-year screening US and mammogram visit.