PCN221 Treatment Patterns Including Adherence/Persistence with Cyclin-Dependent Kinase 4&6 Inhibitors (CDK4&6I) Among US Commercially Insured Women with Metastatic Breast Cancer (MBC)

We conducted a retrospective analysis using a commercially insured US population to describe patient characteristics and treatment patterns including adherence/persistence among women with mBC using oral CDK4&6i. The HealthCore Integrated Research Database (HIRD®) containing claims and enrollment data from a large commercial US payer was used to identify adult women with mBC and CDK4&6i fills (abemaciclib, palbociclib, ribociclib) between Jan-2012 and Jun-2018. Patients were required to have ≥6 months of health plan enrollment before (baseline) and after (follow-up) the earliest CDK4&6i fill. Patients with other kinase inhibitor use or claims for other primary cancers at baseline were excluded. Metastases were identified via ICD-9/10-CM codes. Line of therapy was based on presence/absence of medication claims at baseline. Adherence was measured via proportion of days covered (PDC≥80%) over 6-months follow-up, and a 60-day gap was used for discontinuation. No statistical testing was conducted. Among 1,748 CDK4&6i users mean (standard deviation, SD) age was 60 (11.4) years. Approximately 19% were enrolled in managed Medicare plans. At baseline, metastases were found most frequently in the bone (77%), followed by lymph nodes (33%), liver (21%), and lung (19%). Approximately 72% used CDK4&6i as 2nd-line+ treatment, usually following endocrine therapy (62%) or chemotherapy (18%). Mean (SD) number of concomitant all-cause drug classes (excluding CDK4&6i) over baseline and follow-up was 9 (4.9). Mean (SD) PDC to CDK4&6i was 0.75 (0.24) and 58% of patients were classified as adherent; 23% of patients discontinued over 6-months follow-up and among those, mean (SD) time to discontinuation was 67 (33.2) days. Over a six-month period approximately two-thirds of CDK4&6i initiators were adherent and a quarter discontinued. We observed high levels of polypharmacy. Future research is needed to investigate longer-term adherence/persistence and factors that influence these measures to enable development of solutions to optimize outcomes for patients.