Association of Changes in Missouri Law for Breast Cancer Screening, Screening Rates, and Use of Digital Breast Tomosynthesis.

Objective: To estimate the association of Missouri law changes expanding mammography coverage to include annual screening from age 40 (previously biennial from age 50), digital breast tomosynthesis (DBT) on overall screening rates, and use of DBT.

Methods: This retrospective study (2015-2022) used a national claims database (Inovalon Insights, LLC). A difference-in-differences approach was used in logistic regression models to assess the association of changes in Missouri law with women's likelihood of screening, and for those screened, the likelihood of receiving DBT. Within-Missouri models compared Medicaid and commercial patients to beneficiaries of federally regulated Medicare Advantage (MA) plans. The association was further tested via a comparison of Missouri patients to their counterparts in Missouri border states without a coverage change.

Results: There were 1,008,881 unique women (41.4% [417,835] in Missouri). After the Missouri law change, women with Medicaid (odds ratio [OR]: 1.45; 95% confidence interval [CI]: 1.36-1.55) and commercial insurance (OR: 1.05; 95% CI: 1.01-1.10) had a greater increase in likelihood of screening mammography compared to MA women whose coverage is based on federal law. Medicaid women with mammography had a higher likelihood of DBT for both within-Missouri (OR: 2.31; 95% CI: 2.01-2.66) and border-state (OR: 1.24; 95% CI: 1.22-1.27) comparisons. Commercially insured women likewise had a relative increase in likelihood of receiving DBT.

Conclusion: Changes in Missouri law expanding breast cancer screening coverage were strongly associated with increased screening rates among Medicaid patients as well as increased likelihood of DBT among screened patients, for both Medicaid and commercially insured patients.