Impact of Late Dosing on Testosterone Suppression with Two Different Leuprolide Acetate Formulations: In Situ Gel and Microsphere - An Analysis of US Clinical Data.

Abstract

PURPOSE: Non-adherence to dosing schedules for androgen deprivation therapy (ADT) increases risk of testosterone (T) escape for prostate cancer (PCa) patients. Two approved formulations of leuprolide acetate (LA), the most commonly prescribed ADT in the US, use different extended-release delivery technologies: an in situ gel and microspheres. We evaluated the prevalence and impact of late dosing on T suppression for Gel-LA and Msphere-LA. MATERIALS AND METHODS: We retrospectively analyzed records of PCa patients treated with Gel-LA or Msphere-LA. Analyses used 2 definitions of \u27month\u27: \u2728-day\u27 (late dosing after day 28, 84, 112 or 168) and \u27extended\u27 (late dosing after day 32, 97, 128 and 194). Frequencies of late dosing and associated T values were calculated. RESULTS: 2,038 patients received Gel-LA and 8,360 received Msphere-LA. More than 80% and 27% of injections were late for 28-day and extended month, respectively. For 28-day month late injections, 10% (Gel-LA) and 14% (Msphere-LA) of T values were \u3e50ng/dL, and 25% (Gel-LA) vs. 33% (Msphere-LA) were \u3e20ng/dL. For extended month, 18% (Gel-LA) vs. 25% (Msphere-LA) were \u3e50ng/dL, and 34% (Gel-LA) vs. 44% (Msphere-LA) were \u3e20ng/dL. Msphere-LA was 1.5x more likely to have T \u3e50/20ng/dL vs. Gel-LA. Least-square mean T was 34ng/dL (Gel-LA) vs. 46ng/dL (Msphere-LA) for 28-day month, and 48ng/dL (Gel-LA) vs. 76ng/dL (Msphere-LA) for extended month. CONCLUSIONS: Leuprolide acetate therapies were frequently administered late. Gel-LA demonstrated higher rates of T ≤50ng/dL and ≤20ng/dL than Msphere-LA. Optimal T suppression can impact PCa progression and patient survival and differences in extended-release technology for ADT appear relevant