Impact of the California Breast Density Law on Screening Breast MR Utilization, Provider Ordering Practices, and Patient Demographics.

PURPOSE: To assess the impact of California's Breast Density Law (BDL) on MRI utilization and clinician ordering practices.

MATERIALS AND METHODS: Our institutional review board approved this study that retrospectively compared the ordering pattern for screening breast MRI examinations in the 30-month period before and after the BDL was enacted. Examinations were subcategorized into those with breast density mentioned as an examination indication. Patients were classified into (1) high risk; (2) above average risk, defined but not quantified; and (3) undefined or average risk. χ2 test or Fisher's exact test was used to compare MRI utilization, use of breast density as an indication, patient demographics, and provider characteristics.

RESULTS: Screening MRI examinations with breast density as the indication increased from 8.5% (32 of 376) to 21.1% (136 of 646, P < .0001) after BDL. When high-risk patients were excluded, the increase was from 8% to 17.2% (P < .0001). Patient demographics before and after BDL were, by race: white 71.8% versus 71.2%; Asian 6.4% versus 10.5%; black 3.7% versus 3.1%; American Indian 0.3% versus 1.4%; Native Hawaiian or Pacific Islander 1.6% versus 1.7%; by ethnicity: Hispanic or Latino 10.6% versus 7.9%. Before and after BDL, predominantly female providers (81.4% and 77.4%, P = not significant [NS]) and specialists (62.5% and 63.5%, P = NS) ordered the majority of breast MRI examinations compared with males (18.6% and 22.6%, P = NS).

CONCLUSION: Screening breast MRI utilization for non-high-risk women more than doubled after the California BDL went into effect. BDL has had an impact on MRI utilization, and its clinical value for changing outcomes deserves further study.