Survival benefit in women with BRCA1 mutation or familial risk in the MRI screening study (MRISC)

Adding MRI to annual mammography screening improves early breast cancer detection in women with familial risk or BRCA1/2 mutation, but breast cancer specific metastasis free survival (MFS) remains unknown. We compared MFS of patients from the largest prospective MRI Screening Study (MRISC) with 1:1 matched controls. Controls, unscreened if<50 years, and screened with biennial mammography if 50 years, were matched on risk category (BRCA1, BRCA2, familial risk), year and age of diagnosis. Of 2,308 MRISC participants, breast cancer was detected in 93 (97 breast cancers), who received MRI <2 years before breast cancer diagnosis; 33 BRCA1 mutation carriers, 18 BRCA2 mutation carriers, and 42 with familial risk. MRISC patients had smaller (87% vs. 52% <T2, p<0.001), more often node negative (69% vs. 44%, p=0.001) tumors and received less chemotherapy (39% vs. 77%, p<0.001) and hormonal therapy (14% vs. 47%, p<0.001) than controls. Median follow-up time was 9 years (range 0-14). Breast cancer metastasized in 9% (8/93) of MRISC patients and in 23% (21/93) of controls (p=0.009). MFS was better in MRISC patients overall (log-rank p=0.008, HR 0.36, 95% CI 0.16-0.80), with familial risk (log-rank p=0.024, HR: 0.21, 95% CI 0.04-0.95), and in BRCA1 mutation carriers (log-rank p=0.055, HR 0.30, 95% CI 0.08-1.13). MFS remained better in MRISC patients after lead time correction (log-rank p=0.020, HR 0.40, 95% CI 0.18-0.90). Overall survival was non-significantly better in MRISC patients (log-rank p=0.064, HR 0.51, CI 0.24-1.06). Annual screening with MRI and mammography improves metastasis free survival in women with BRCA1 mutation or familial predisposition. What's New? Adding MRI to annual mammography screening improves early breast cancer detection in women with familial risk or BRCA1/2 mutation. The impact of MRI screening on metastasis free survival remains unknown, however. For ethical reasons, all of the relevant studies so far have had a non-randomized design. To address this issue, here the authors compare breast cancer patients in the largest prospective MRI Screening Study (MRISC) with controls matched for risk group, year of diagnosis, and age at diagnosis. Annual screening with MRI and mammography improves breast cancer specific metastasis free survival significantly in women with BRCA1 mutation or familial predisposition.