The effects of oral anticancer parity laws on out-of-pocket spending and adherence among commercially insured patients with chronic myeloid leukemia

BACKGROUND: Over the past 12 years, 43 states and Washington DC have implemented oral anticancer medication parity laws in response to the burden of pharmacy cost sharing. Parity laws are designed to provide equal coverage and cost sharing between orally and parenterally administered anticancer medications for patients in commercial, fully insured health plans (FIHPs). However, there is considerable state-level variation in the requirements to achieve compliance with parity laws, and the clinical and economic effectiveness of parity is not fully known. OBJECTIVES: To (a) understand the impact of parity laws on out-of-pocket (OOP) spending and adherence to tyrosine kinase inhibitors (TKI) among commercially insured patients with chronic myeloid leukemia (CML) and (b) compare these effects across states with and without per prescription or per 30-day OOP spending limits as part of their parity laws. METHODS: Patients aged 18-64 years with CML, at least 1 pharmacy claim for a TKI, and residence in a state that implemented oral anticancer parity legislation between January 1, 2007, and January 1, 2017, were identified from the IBM MarketScan Commercial Claims and Encounters database. A propensity score-weighted difference-in-difference approach was used to measure the impact of parity on OOP spending and adherence in the 6 months after the first pharmacy claim for a TKI (index date) for patients enrolled in FIHPs (subject to parity) and self-funded health plans (SFHPs; exempt from parity). OOP spending was standardized to a 30-day equivalent amount and adjusted to 2017 US dollars. Adherence was assessed using the proportion of days covered (PDC), and patients were categorized as adherent with PDC >= 0.80. RESULTS: Of 1,887 patients initiating a TKI before or after their state's parity law, 678 (35.9%) were enrolled in FIHPs (480 before vs 198 after parity), and 1,209 (64.1%) were enrolled in SFHPs (688 before vs 521 after parity). Implementation of parity laws was not associated with any changes in mean OOP spending; however, it was associated with a reduced likelihood of paying $ 0 per 30 days across all states (adjusted difference-in-difference [aDD] OR = 0.662; 95% CI = 0.535-0.820) and states without OOP spending limits (aDD OR = 0.654; 95% CI =0.508- 0.848), but not in states with limits. Nonsignificant but directionally opposite changes at each end of the OOP spending distribution were observed for states with and without OOP spending limits, with increased spending observed at the 75th, 90th, and 95th percentiles in states without limits. Mean PDC and adherence showed a nonsignificant increase among FIHP and SFHP patients across all states, states with limits, and states without limits. CONCLUSIONS: Oral anticancer parity laws are not associated with reduced OOP spending or improved adherence in a commercially insured sample of patients with CML. These findings were consistent for states that included OOP spending limits as a component of their parity laws.