title: Efficacy over time of LHRH analogs in the treatment of PCa--a prospective analysis using serum testosterone to determine dosing intervals.
abstract: OBJECTIVE
  To examine the duration of serum testosterone and prostate-specific antigen suppression after each dose of a 4-month depot leuprolide acetate for 18 months and to assess the potential for using serum testosterone as a guide for redosing the luteinizing hormone-releasing hormone analogs instead of using fixed dosing intervals. Luteinizing hormone-releasing hormone analogs are well established for the treatment of prostate cancer (PCa). However, many open questions remain regarding the optimal dosing.
  
  
  METHODS
  Thirteen patients with PCa were enrolled in a longitudinal study. Serum testosterone levels were obtained at baseline and then monthly beginning 4 months after the first injection and every 2 months after the subsequent injections, for a total of 18 months. The median number of days from injection to the first serum testosterone level > or = 50 ng/dL was estimated using the Kaplan-Meier product-limit method.
  
  
  RESULTS
  The median duration of effect was 159, 189, and 163 days for the first, second, and third treatment cycle, respectively. The prostate-specific antigen values from entry to completion decreased in all subjects. The total number of injections was reduced in all but one subject who completed the 18-month trial. One patient developed hormone-refractory PCa.
  
  
  CONCLUSIONS
  Serum testosterone measurement might be a useful method for redosing luteinizing hormone-releasing hormone analogs. Using testosterone levels to determine the time of reinjection has a significant economic impact. Monitoring serum testosterone not only helps to identify patients who fail to achieve testosterone suppression but also provides close monitoring for the potential development of hormone-refractory PCa.
authors.affiliation: Department of Surgery, Section Urology and Department of Internal Medicine, St. Joseph Mercy Hospital, Ann Arbor, Michigan 48106, USA.
authors.forename: S
authors.initials: S
authors.lastname: Greil
authors.forename: E A
authors.initials: EA
authors.lastname: Robinson
authors.forename: B
authors.initials: B
authors.lastname: Singal
authors.forename: E
authors.initials: E
authors.lastname: Kleer
mesh_terms: D000368:Aged; D018931:Antineoplastic Agents, Hormonal / Q000008:administration & dosage*; D016903:Drug Monitoring / Q000379:methods; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives*; D006801:Humans; D016729:Leuprolide / Q000008:administration & dosage*; D008297:Male; D011446:Prospective Studies; D011471:Prostatic Neoplasms / Q000097:blood* / Q000188:drug therapy*; D013739:Testosterone / Q000097:blood*; D013997:Time Factors
chemical_list: D018931:Antineoplastic Agents, Hormonal; D007987:Gonadotropin-Releasing Hormone; D013739:Testosterone; D016729:Leuprolide