Dense Breast Laws Linked to More Supplemental Imaging

Key Takeaways

• In a large US commercially insured screening mammography population, 9% of women received supplemental ultrasonography and 0.6% received magnetic resonance imaging within 6 months.
• Dense breast notification mandates were associated with higher supplemental ultrasonography and MRI use after screening mammography.
• Insurance coverage laws were associated with a larger increase in supplemental ultrasonography use than notification mandates alone.
• Within states with notification mandates, notices that mentioned supplemental screening were associated with higher supplemental ultrasonography use.
• Targeted notification to women with dense breasts was also associated with higher supplemental imaging use, while MRI remained uncommon overall.

After a screening mammogram, next steps can hinge not only on the imaging result but also on whether a patient receives a dense breast notice, what that notice says, and whether supplemental imaging is covered. Those differences can change both the information patients receive and the financial barriers they face when additional imaging is considered. In a large US claims cohort of commercially insured women, investigators examined how those policy differences tracked with real-world supplemental imaging use.

Using the MarketScan Commercial Claims and Encounter Database from January 1, 2008, through December 31, 2019, Kang et al in JAMA Network Open conducted a retrospective, quasi-experimental cohort study of 12,555,082 women aged 40 to 64 years undergoing screening mammography who had at least 6 months of continuous enrollment after the index examination. A 9-month washout excluded prior mammography or breast cancer-related diagnoses. Investigators evaluated notification laws and insurance coverage laws by state effective date, limited exploratory analyses of notice design to states with notification mandates, and defined the primary outcome as receipt of supplemental ultrasonography or magnetic resonance imaging (MRI) within 6 months after screening mammography. The analysis used an extended difference-in-differences approach with state and time fixed effects, with a 7-month sensitivity window and an event-study model as robustness checks.

In the adjusted dense breast legislation and supplemental imaging analysis, notification mandates were associated with higher supplemental ultrasonography use (odds ratio [OR], 1.09; 95% confidence interval [CI], 1.08-1.10) and higher MRI use (OR, 1.09; 95% CI, 1.06-1.12). The authors characterized those associations as small absolute increases after screening mammography.

Insurance coverage laws were associated with higher supplemental ultrasonography use (OR, 1.88; 95% CI, 1.86-1.90), corresponding to an absolute increase of 4.7 percentage points, or 47 additional ultrasonography examinations per 1000 women. Within states with notification mandates, notices that mentioned supplemental screening were also associated with higher ultrasonography use (OR, 2.84; 95% CI, 2.81-2.86), while targeted notification to women with dense breasts was also associated with higher ultrasonography and MRI use. In the event-study analysis of dense breast notification laws and supplemental ultrasonography, estimates before policy implementation were near zero and turned positive afterward, a temporal pattern consistent with the main ultrasonography finding.

The analysis reports associations in imaging use rather than cancer detection, interval cancers, mortality, or patient-level screening benefit. The authors noted possible residual confounding from time-varying state factors, incomplete capture of legislative nuances, restriction of the feature analyses to states with notification laws, limited generalizability beyond commercially insured women aged 40 to 64 years, and claims-based inability to reliably separate screening from diagnostic ultrasonography or MRI. The 6- and 7-month outcome windows reflected the lack of standardized timing for supplemental imaging after mammography, so the findings remain most informative about utilization patterns rather than clinical benefit.

Overall, the authors reported that both notification mandates and insurance coverage laws were associated with greater supplemental ultrasonography use after screening mammography, with a larger coverage-related signal, while notification mandates were also associated with higher MRI use. Supplemental imaging nevertheless remained uncommon overall, and the analysis did not show whether higher use improved clinical outcomes.

Clinician Questions

How did the investigators separate the effects of dense breast notification laws from insurance coverage laws after screening mammography?

The analysis evaluated dense breast notification laws and insurance coverage laws independently by their state effective dates in an extended difference-in-differences design, comparing within-state changes before versus after implementation with contemporaneous changes in states without the law. In commercially insured women aged 40 to 64 years undergoing screening mammography, that approach separated the 2 policy types analytically rather than proving causality.

Why might the reported supplemental imaging rates after mammography overstate screening-specific use?

Claims-based Current Procedural Terminology coding could not reliably distinguish screening from diagnostic ultrasonography or magnetic resonance imaging, so the supplemental imaging outcome may have included diagnostic examinations. The authors said that limitation could overestimate screening-specific use and could also distort the observed associations with dense breast legislation.

Do these dense breast legislation findings apply to Medicare, Medicaid, or uninsured women?

The study population was limited to commercially insured women aged 40 to 64 years, and the authors said the findings may not generalize to Medicare, Medicaid, other public insurance programs, or uninsured populations. State insurance mandates also may not apply uniformly to public or federally regulated coverage, and those groups may face different financial, structural, or geographic barriers to supplemental imaging.

Did supplemental ultrasonography trends shift only after dense breast notification laws took effect?

In the event-study sensitivity analysis, supplemental ultrasonography estimates before implementation were small and centered near zero, while estimates after implementation became positive. According to the authors, that temporal pattern was consistent with the main association between notification laws and higher ultrasonography use.