Abstract
BACKGROUND: Hormone receptor (HR)-negative, HER2-positive (also called HER2-enriched) breast cancer has no worse prognosis than other breast cancers if it is treated with HER2-targeted therapy. Medicaid expansion under the Affordable Care Act (ACA) has been shown to be associated with improved access to care and outcomes for many cancers, but its association with receipt of care for HR-negative, HER2-positive breast cancer is unknown. We examined the association of Medicaid expansion with receipt of guideline-concordant treatment, time to treatment initiation, and survival among nonelderly women newly diagnosed with HR-negative, HER2-positive breast cancer. PATIENTS AND METHODS: Women aged 18 to 62 years newly diagnosed with HR-negative, HER2-positive breast cancer between 2010 and 2018 were identified from the National Cancer Database. Outcomes included receipt of stage-based guideline-concordant treatment, timely initiation of treatment (<30 days, <60 days, <90 days from diagnosis), and stage-specific 2-year overall survival. A difference-in-differences (DID) analytic approach compared outcome changes following Medicaid expansion in expansion versus nonexpansion states. Multivariable linear probability models were used to estimate treatment outcomes, and flexible parametric survival models were used to evaluate survival, adjusting for sociodemographic and clinical confounders. RESULTS: A total of 31,401 patients were included. Medicaid expansion was associated with an increase of 0.58 percentage points (ppt; 95% CI, 0.01-1.16) in receipt of guideline-concordant treatment overall, a 2.43-ppt (95% CI, 0.68-4.18) increase in initiating guideline-concordant treatment <60 days after diagnosis, and a 1.17-ppt (95% CI, 0.02-2.32) increase in 2-year survival rate. The increase in 2-year survival associated with Medicaid expansion was most prominent for patients with stage III disease (DID, 3.81; 95% CI, 0.82-6.80). CONCLUSIONS: Medicaid expansion was associated with improved care and survival for patients with HR-negative, HER2-positive breast cancer, an aggressive cancer type for which prognosis largely depends on access to effective treatment.