Adherence to Injectable and Oral Hormone Therapies in Advanced Prostate Cancer as Measured by Proportion of Days Covered

December 2021 Vol 12, No 12
Tao Jiang
Charles River Associates, Boston, MA
Robert Dufour
Myovant Sciences, Inc., Brisbane, CA
Eddie Li
Charles River Associates, Boston, MA
Janis Pruett
Myovant Sciences, Inc., Brisbane, CA

Background: Androgen deprivation therapy (ADT) with luteinizing hormone-releasing hormone (LHRH) agents is the mainstay of advanced prostate cancer (PC) care. Androgen receptor antagonists and/or androgen synthesis inhibitors (ARA/ASIs) are also frequently used. Most ADTs are available as injectables while ARA/ASIs are orals. It is believed that injectable therapies lead to high medication adherence. A recent article examined timeliness of ADT injections and concluded some patients experience long delays (>2 weeks) between injections, often leading to higher testosterone levels.

Objective: Assess adherence to injectable ADTs and oral ARA/ASIs.

Methods: Men diagnosed with PC and treated with either an ADT (degarelix, goserelin, leuprolide acetate, triptorelin) or ARA (bicalutamide, enzalutamide)/ASI (abiraterone) were identified in a large administrative US claims data set (2010-2019). Continuous enrollment of 12 months before and after treatment initiation and ≥2 claims for ADTs or ARA/ASIs were required for inclusion. Proportion of days covered (PDC), a standard measure of adherence for oral medications using data elements from pharmacy claims, was adjusted to the data elements found on medical claims. Delays between ADT injections and ARA/ASI fills were measured. The results are reported by agent.

Results: Of 15,861 ADT-treated and 9004 ARA/ASI- treated patients, 12,540 (79.1%) and 7815 (86.8%), respectively, with the required data elements were included. The median treatment duration ranged from 103 (degarelix) to 429 (leuprolide acetate) days for ADTs and 229 (bicalutamide) to 373 (enzalutamide) days for ARA/ASIs. Mean PDC ranged from 0.91 (SD: 0.07) to 0.94 (0.04) for ADTs and 0.90 (0.10) to 0.92 (0.11) for ARA/ASIs. Examination of dose delay indicated that 25% of 3-, 4-, or 6-month ADT doses (4350/17,400 doses) were administered late (≥12 days). In contrast, 25% of ARA/ASI refills (14,995/59,983 refills) were ≥3 days late.

Conclusions: Adherence, using PDC, can be assessed for injectable therapy documented on medical claims for most patients. The PDC rates for ADTs were comparable to those obtained for oral ARA/ASIs. Overall, men diagnosed with PC and treated either with an ADT or ARA/ASI were adherent (PDC >80%) to their treatment. However, a quarter of the injectable doses were delayed ≥12 days from their targeted date, while ARA/ASIs demonstrated shorter refill delays. This type of adherence analysis should be applied to emerging advanced PC treatments.

Sponsorships: Myovant Sciences GmBH, in collaboration with Pfizer, Inc.

(Encore: Accepted to AMCP Nexus 2021)

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