MRI versus mammography plus ultrasound in women at intermediate breast cancer risk: study design and protocol of the MRIB multicentre randomized controlled trial

BackgroundIn women at high/intermediate lifetime risk of breast cancer (BC-LTR), contrast-enhanced magnetic resonance imaging (MRI) added to mammography {+/-}ultrasound (Mx{+/-}US) increases sensitivity but decreases specificity. An alternative strategy, MRI alone, potentially more cost-effective, has never been explored. This study aims to assess the characteristics of women who participated in a randomized trial offering MRI alone. MethodsIn this feasibility multicentre randomized controlled trial we compared MRI alone versus Mx+US in women at intermediate BC-risk (allocation ratio 1:1). Eligible women were aged 40 -59, with a 15-30% LTR and/or extremely dense breasts. Two screening rounds per woman were planned in ten centres experienced in MRI screening. Primary endpoint: rate of cancers detected in the two arms after 5 years of follow-up. Secondary endpoints: distribution of the risk profiles among the women enrolled in the trial; distribution of pathological stages and histology of cancers detected; interval cancer rate in the two arms. ResultsFrom 07/2013 to 11/2015, 1,254 women (mean age 47 years) were enrolled: 624 were assigned to Mx+US, 630 to MRI. Most of them were aged below 50 (72%) and premenopausal (45%), 52% used oral contraceptives. Among postmenopausal women, 15% had used hormone replacement therapy. Breast and/or ovarian cancer in mother and/or sisters were reported by 37% of enrolled women, extreme breast density was recorded for 79%, 41% had a 15-30% BC-LTR. ConclusionsThe distribution of BC-risk profile major determinants (breast density and family of breast and ovarian cancer) of enrolled women varied across centres. Trial registrationNCT02210546 Key pointsO_LIMammography plus ultrasound are commonly used to screen women with dense breasts C_LIO_LISupplemental ultrasound increases BC detection rate but also false-positives and potential overdiagnosis C_LIO_LIWhether increased BC detection by US translates into reduced mortality is unknown C_LIO_LIMRI alone could be more risk- and cost-effective than mammography plus ultrasound C_LI