title: Prostate cancer: finasteride extends PSA doubling time during intermittent hormone therapy.
abstract: OBJECTIVE
  Finasteride has been shown to prolong the time off-treatment in men with prostate cancer during intermittent androgen suppression therapy, but it is not clear whether this results from an increase in prostate-specific antigen (PSA) doubling time or a delay in PSA responsiveness to regained testicular function. In the following study, we distinguish between these two possibilities and consider how the effectiveness of finasteride might be altered if androgens are synthesized within the malignant cell rather than the testis.
  
  
  METHODS
  Six patients were followed on intermittent androgen suppression for intervals ranging from 7 to 10 years. The effects of finasteride on the length of the off-treatment period in at least one cycle in each patient were measured with monthly determinations of serum PSA and testosterone and calculation of PSA doubling time using linear regression analysis.
  
  
  RESULTS
  Administration of finasteride was associated with a reduction in the rate of increase of serum PSA in the off-treatment period of any given cycle within a sequence of 5. In a total of 15 cycles, finasteride extended PSA doubling time from a mean of 7.7 weeks (n = 11, range 2.3-29.8 weeks) to a mean of 45.1 weeks (n = 6, range 13.8-99.7 weeks). One patient was characterized by an apparent pseudo-resistance to finasteride in the 2nd cycle of treatment and another patient by complete resistance to finasteride in the 4th cycle.
  
  
  CONCLUSIONS
  Finasteride can be introduced into any cycle of intermittent androgen suppression with the expectation of an extension of PSA doubling time.
authors.affiliation: The Prostate Centre at Vancouver General Hospital, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Locke
authors.forename: Nicholas
authors.initials: N
authors.lastname: Bruchovsky
mesh_terms: D000230:Adenocarcinoma / Q000097:blood* / Q000188:drug therapy*; D000368:Aged; D018931:Antineoplastic Agents, Hormonal / Q000008:administration & dosage; D018120:Finasteride / Q000627:therapeutic use*; D006801:Humans; D008297:Male; D008875:Middle Aged; D017430:Prostate-Specific Antigen / Q000097:blood* / Q000187:drug effects*; D011471:Prostatic Neoplasms / Q000097:blood* / Q000188:drug therapy*; D012189:Retrospective Studies; D013997:Time Factors
chemical_list: D018931:Antineoplastic Agents, Hormonal; D018120:Finasteride; D017430:Prostate-Specific Antigen