Auditing a Breast MRI Practice: Performance Measures for Screening and Diagnostic Breast MRI

Abstract

Objective Breast magnetic resonance imaging (MRI) is increasingly being used for both screening and diagnostic purposes. While performance benchmarks for screening and diagnostic mammography have been published, performance benchmarks for breast MRI have yet to be established. The purpose of our study was to comprehensively evaluate breast MRI performance measures, stratified by screening and diagnostic indications, from a single academic institution. Subjects and Methods Institutional review board approval was acquired for this HIPAA compliant study. Informed consent was not required. Retrospective review of our institutional database identified all breast MRI examinations performed from 4/1/07 to 3/31/08. After application of exclusion criteria, the following performance measures for screening and diagnostic indications were calculated: cancer detection rate, positive predictive values (PPV), and abnormal interpretation rates. Results The study included 2444 examinations, 1313 for screening and 1131 for diagnostic indications. The cancer detection rates were 14 per 1000 screening breast MRI examinations and 47 per 1000 diagnostic examinations (p-value < 0.00001). The abnormal interpretation rate was 12% (152/1313) for screening and 17% (194/1131) for diagnostic indications (p-value = 0.00008). The positive predictive values of MRI were lower for screening (PPV1 = 12%, PPV2 = 24%, PPV3 = 27%) compared to diagnostic indications (PPV1 = 28%, PPV2 = 36%, PPV3 = 38%). Conclusion Breast MRI performance measures differ significantly between screening and diagnostic MRI indications. Medical audits for breast MRI should calculate performance measures for screening and diagnostic breast MRI separately, as recommended for mammography.

Screening Breast MRI Outcomes in Routine Clinical Practice

“…Using data from 41 facilities across five Breast Cancer Surveillance Consortium imaging registries, Lee et al (34) found a screening breast MRI AIR of 10.5% if BI-RADS category 3 examinations were excluded, and 21.0% if they were included. Niell et al (20) found a similar abnormal interpretation rate of 12% when BI-RADS category 3 lesions were excluded.…”

“…As radiologists become more experienced in the interpretation of MRI, the BI-RADS category 3 rate will likely decrease. This was demonstrated in the Niell et al study, where 21% of the screening MRI examinations during the study interval were assessed as BI-RADS category 3, but in subsequent years the BI-RADS category 3 rate at their institution fell to less than 5% (20). …”

“…To date, it has not been known whether the BI-RADS metrics would be applicable in routine practice in the United States outside of the research setting, and with a spectrum of patients at elevated risk. Only one prior study has assessed breast MRI audit performance measures in broad practice, using MRI examinations from 2007 to 2008 (20). Our clinical practice audit, evaluating screening examinations from 2010 to 2013, demonstrated that cancer detection rate, median invasive cancer size, PPV2, and PPV3 all fell within the ACR BI-RADS MRI benchmarks (23), supporting their broader appropriateness for routine practice (Table 3) in the United States.…”

“…Our PPV2 (biopsy recommended) of 21.6% met the benchmark of 15%, and our PPV3 (biopsy performed) of 23.8% was in the benchmark range of 20%–50%. In 2014, Niell et al published the results of an audit of their breast MRI practice (20). Their PPV2 and PPV3 for screening breast MRI were 24% and 27% respectively, similar to our results and additionally supporting the use of the BI-RADS benchmarks.…”

“…The NCCN states that the utility of MRI in follow-up screening of women with prior breast cancer is undefined (18). However, recent data suggest that particularly those patients with a personal history of treated breast cancer constitute a significant proportion of patients being screened with breast MRI (19,20). …”