Abstract P6-13-01: MRI breast cancer screening compared to mammography in women with a familial risk: A multicenter randomized controlled trial
Authors: Tilanus-Linthorst MM , Saadatmand S , Geuzinge AH , Rutgers EJ , Mann R , de Roy van Zuidewijn DB , Zonderland HM , Tollenaar RA , Lobbes MB , Ausems MG , van 't Riet M , Hooning MJ , Mares-Engelbert I , Luiten EJ , Heijnsdijk EA , Verhoef C , Karssemeijer N , Oosterwijk JC , Obdeijn I-M , de Koning HJ 
Published: May 2019

Abstract
Background: Screening guidelines for women with a family history of breast cancer without a known causative gene mutation differ per country. No randomized controlled trial has been performed to assess the optimal screening strategy for these women.
Methods: In twelve centers, 1355 women aged 30–55 years with a cumulative lifetime risk of ≥20% without a BRCA1/2 mutation were randomized into two arms. From January 2011 until December 2017, women in the MRI-arm received yearly MRI-screening, clinical breast examination (CBE), and mammography every other year; and in the Mx-arm yearly mammography and CBE. Outcomes were number and stage of detected breast cancers, sensitivity, specificity and positive predictive value, and stratified by screening round and by mammographic density.
Results: After on average 4.3 screening rounds per woman, in the MRI-arm (N=675) compared to the Mx-arm (N=680) more breast cancers were detected (41 versus 14, p&lt;0.001), invasive cancers were smaller (median size 8 versus 17 mm, p=0.006) and less often node positive (20% versus 71.4%, p=0.019)(Table). In the MRI-arm, sensitivity was slightly higher (95.1% versus 92.9%, p=1), and specificity significantly lower (82% versus 90.1%, p&lt;0.001), compared to the Mx-arm. After two rounds, specificity improved for both modalities (87.1% for MRI; 93.0% for Mx; p&lt;0.001) and no ≥T2 tumors or interval cancers occurred in the MRI-arm. All tumors ≥T2 were in the two highest density categories. MRI detected more small invasive tumors than Mx across all density categories.
Conclusions: In real-life practice the MRI-arm detected more, relevantly smaller, and far more often node negative tumors, and also at low density in women with a familial risk for breast cancer.
Table 1Characteristics of participating women at baseline and of the detected breast cancers, according to study armParticipantsMRI-arm n=675Mx-arm n=680MRI-arm vs. Mx-arm p-valueMean age yr ± SD44.6 ± 6.244.7 ± 6.3 Premenopausal512 (76%)505 (74%) Previous Mx ≤ 2 yr536 (79 %)542 (80%) Previous Mx &gt; 2 years ago23 ( 3%)29 ( 4%) Previous MRI ≤ 2 years ago62 ( 9%)81 (12%) Previous MRI &gt; 2 years ago91 (14%)89 (13%) BI-RADS density category* I (entirely fat)88 (13%)92 (14%) II (scattered densities)248 (37%)229 (34%) III (heterogeneously dense)238 (35%)243 (36%) IV (extremely dense)98 (15%)102 (15%) Mean age at cancer detection49,6 ± 7.049,8 ± 4,70.74No cancer – no. (%)634 (94%)666 (98%) Invasive breast cancers – no. (%)25 (4%)7 (1%)&lt;0.001 (noBC/inv BC/DCIS)DCIS – no. (%)16 (2%)7 (1%) Median size of invasive cancers8 mm17 mm0.006T1a/b15 (60%)1 (14%) T1c7 (28%)4 (57%)0.078 (T1a-b/T1c/≥ T2)≥ T23 (12%)2 (29%) Node pos5 (20%)5 (71%)0.019 (N+/-)Node negative20 (80%)2 (29%) DCIS grade 15 (31%)2 (29%) DCIS grade 28 (50%)4 (57%)1 (dcis gr1,2,3)DCIS grade 33 (19%)1 (14%) *Determined by radiologists, according to the fourth ACR BI-RADS edition
Citation Format: Tilanus-Linthorst MM, Saadatmand S, Geuzinge AH, Rutgers EJ, Mann R, de Roy van Zuidewijn DB, Zonderland HM, Tollenaar RA, Lobbes MB, Ausems MG, van 't Riet M, Hooning MJ, Mares-Engelbert I, Luiten EJ, Heijnsdijk EA, Verhoef C, Karssemeijer N, Oosterwijk JC, Obdeijn I-M, de Koning HJ. MRI breast cancer screening compared to mammography in women with a familial risk: A multicenter randomized controlled trial [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-13-01.