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The prostate cancer prevention trial

Created: 17/3/2007
Updated: 17/3/2007

 

The influence of finasteride on the development of prostate cancer
Ian M Thompson, Phyllis J Goodman, Catherine M Tangen, M Scott Lucia, et al.
NEJM Jul 17, 2003. 349; 3: 215-224

Introduction

  • The management of prostate cancer, the most common nondermatologic neoplasm in men in the United States, has focused on early diagnosis and treatment-prevention, however, may be a more effective approach
  • Androgens influence the development of prostate cancer
  • Finasteride inhibits 5alpha-reductase, which converts testosterone to the more potent dihydrotestosterone
  • The aim of the current study was to determine whether finasteride reduces the prevalence of prostate cancer among initially healthy men during a seven-year study period

Methods

  • 18,882 men, 55 years or older, normal DRE, AUA symptom score less than 20 and PSA = 3.0ng.ml included
  • After 3 month run-in period with a placebo men were randomly assigned to finasteride (5 mg per day) or placebo
  • The planned duration of treatment was seven years
  • The men underwent annual digital rectal examinations and measurements of PSA
  • Biannually seen for repeat perscription, and recording of clinically significant medical conditions and side effects
  • Every three months, the men were contacted by telephone for the collection of data on interim medical events
  • Prostate biopsy was recommended if the annual PSA level, adjusted for the effect of finasteride, exceeded 4.0 ng per ml or if DRE was abnormal
  • The primary end point was the prevalence of prostate cancer during the seven years of the study
  • At the end of seven years, all men who had not been given a diagnosis of prostate cancer were offered an end-of-study prostate biopsy – This was due to the effect of finasteride on PSA levels (which is the primary method of screening for prostate cancer)

Results

  • 15 months before the anticipated completion of the study, the study was terminated as the objective had been met and the conclusions were extremely unlikely to change with additional diagnoses of prostate cancer and end-of-study biopsy results
  • The rate of diagnosis of prostate cancer or end-of-study biopsy was 59.6 % in the finasteride group and 63.0 % in the placebo group (P<0.001)
  • Prostate cancer was detected in 803 of the 4368 men in the finasteride group (18.4 percent) and 1147 of the 4692 men in the placebo (24.4 percent), who had data for the final analysis (not all proceeded to biopsy)
  • Represents a 24.8 percent reduction in prevalence over the seven-year period (95 percent confidence interval, 18.6 to 30.6 percent; P<0.001).

  • Tumours of Gleason grade 7, 8, 9, or 10 were more common in the finasteride group than in the placebo group, P=0.005
    • 280 of 757 tumours - 37.0 % (finasteride) vs 237 of 1068 tumours - 22.2 % (placebo), P<0.001
  • Sexual side effects were more common in finasteride-treated men
  • Urinary symptoms were more common in men receiving placebo

Discussion

  • This high rate and the unpredictable biology of prostate cancer make prevention of the disease an appealing strategy
  • Finasteride is an attractive chemopreventive agent, because it inhibits the conversion of testosterone to the more potent androgen dihydrotestosterone within the prostate and has low toxicity
  • High-grade disease was noted in 6.4 percent of the men in the finasteride group, as compared with 5.1 percent of those in the placebo group
  • One possible explanation for this difference is a grading bias: histologic changes that mimic those of high-grade disease are caused by androgen-deprivation therapy-whether this effect occurs with finasteride is however, uncertain
  • However, finasteride may induce high-grade tumours by reducing the level of intracellular dihydrotestosterone within the prostate - Evidence exists that the prostate tumours that develop in men with low testosterone levels have higher Gleason grades and worse outcomes than the prostate cancers that develop in men with normal testosterone levels
  • Furthermroe, finasteride may also select for high-grade tumours by selectively inhibiting low-grade tumours
  • Tumours detected on biopsies performed for cause were similar to those that are detected in clinical practice by screening of the PSA level and digital rectal examination. The clinical significance of cancers found in the end-of-study biopsies (those not performed for cause) is unknown
  • Eligibility criteria for enrollment in the study selected for low-risk men with an expected lifetime incidence of prostate cancer of 16.7 % and a rate of death from prostate cancer of 3 to 4 %
  • However, the rate cancer detection in the placebo group of 24.4 % is of concern and suggests the possibility of overdiagnosis of disease

Conclusions

  • Finasteride prevents or delays the appearance of prostate cancer, but this possible benefit and a reduced risk of urinary problems must be weighed against sexual side effects and the increased risk of high-grade prostate cancer

Does finasteride cause high-grade prostate cancer?-click here


ArticleDate:20070317
SiteSection: Article
 
   
    
                                            



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