Maintenance of the suppressed level of serum testosterone by administration of three-monthly formulations of luteinizing hormone-releasing hormone agonists at six-month intervals in Japanese patients with prostate cancer: A prospective study.

Abstract

159 Background: Treatment with an LH-RH agonist is a standard alternative to surgical castration for prostate cancer patients. The serum testosterone level is kept at castrate levels continuously during LH-RH agonist therapy in almost all patients (Fujii Y, BJU Int 2008). LH- RH agonists, however, are more expensive than surgical castration, with drugs costing between US $300 and $500 per month in Japan. Recent studies suggest that 3-monthly formulations of LH-RH agonists suppress the serum testosterone levels far longer than the 3-month dosing interval. Methods: A total of 43 Japanese patients with prostate cancer who were treated with 3-monthly LH-RH agonists (23 with 11.25mg leuprolide, and 20 with 10.8 mg goserelin) for one year or longer and whose testosterone levels were kept at castrate level (defined as < 50 ng/dL) were entered into this prospective, longitudinal study. After entry, the 43 men received the same 3-monthly LH-RH agonists at 6-month intervals, and had serum LH and testosterone tests performed at 3-month intervals. Bicalutamide was combined with the LH-RH agonists in 12 of the patients. Results: At entry, median patient age was 74 years (range 59 to 89), median duration of LH-RH agonists treatment was 26 months (12 to 125), and median LH and testosterone levels were <10 ng/dL (<10 to 60) and 5 ng/dL (<5 to 18), respectively. The 43 patients received a total of 162 administrations (median 5, range 1 to 6) of the LH-RH agonists at 6-month intervals, and had a total 335 hormonal tests (median 10, range 2 to12) performed during the median followup period of 30 months. Serum LH and testosterone levels were kept suppressed during the treatment. Of the 43 patients, two had serum testosterone just above the castrate level (54 and 56 ng/dL) once each among their 12 and 8 hormonal assays, respectively. Conclusions: Administration of 3-monthly LH-RH agonists, either leuprolide or goserelin, at 6-month intervals could maintain the castrate level of serum testosterone at least in Japanese prostate cancer patients who have received LH-RH agonists treatment for one year or longer. No significant financial relationships to disclose.