Gel-leuprolide acetate (LA) was shown to suppress testosterone rates over a longer period than Msphere-LA, according to a study presented by Lucio N. Gordan, MD, Florida Cancer Specialists & Research Institute, Gainesville, at the National Comprehensive Cancer Network Virtual Annual Congress.

“Luteinizing hormone-releasing hormone (LHRH) agonists are the most frequently used drugs for androgen deprivation therapy (ADT) in prostate cancer. Achieving and maintaining effective testosterone (T) to levels attained with surgical castration is the cornerstone of ADT for advanced prostate cancer,” wrote Dr Gordan and colleagues.

"However, T levels may rise above castrate level (50ng/dL) between injections, especially if a subsequent dose is delayed,” they continued, adding that late injections were linked to a 4x higher T breakthrough rate and doubled mean T compared to injections that were early/on time. 

With this in mind, Dr Gordan and his team decided to test 2 FDA-approved forms of LA most commonly used in the US with different extended-release systems: in-situ gel technology (Gel-LA; subcutaneous) and microsphere technology (Msphere-LA; intramuscular), to compare the impact of late dosing on T suppression. 

An observational analysis from January 2007 to June 2016 of the US oncology and urology electronic medical records of patients with prostate cancer who received Gel-LA or Msphere-LA injections evaluated the frequency of late dosing, mean T, and rate of T-tests 50ng/dL with late dosing.

A total of 10,398 patients were observed, with 2038 receiving Gel-LA and 8,360 receiving Msphere-LA. With 27% of injections on both drugs administered late, mean T was 48ng/dL in the Gel-LA group and 76ng/dL in the Msphere-LA group. Furthermore, 18% of Gel-LA patients saw T values >50ng/dL, while 25% of patients in the Msphere-LA group had T values >50ng/dL (P <.05)

“As higher T levels, including T escapes, may adversely impact disease progression and survival, clinicians should reassess their dosing schedule compliance policies and use an ADT that optimizes the goal of effective T suppression to castrate levels,” concluded Dr Gordan et al.—Alexandra Graziano

Gordan LN, Atkinson SN, Boldt-Houle DM, et al. Impact of Late Dosing on Testosterone Suppression With Two Different Leuprolide Acetate Formulations: In Situ Gel and Microsphere – an Analysis of US Clinical Data. Presented at: the NCCN 2021 Virtual Annual Conference; March 18-20,2021; Virtual. Abstract CLO21-025.