How effective are five-alpha-reductase inhibitors (5 ARIs) in preventing prostate cancer?
5 ARIs appeared to increase the risk of high-grade prostate cancer (Gleason score of 7-10). Impaired sexual or erectile function (NNH* 25) or endocrine effects, such as gynaecomastia (NNH 50) and reduced libido (NNH 33), were more common with finasteride than placebo. Information was inadequate to assess the impact on mortality. The impact of 5 ARIs on absolute or relative rates of prostate cancer in men who are not being regularly screened is not clear. NNH = Number needed to treat to cause harm in on individual.
Prostate cancer is the second most common cancer in terms of incidence and the third most common in terms of mortality among New Zealand men.1 5 ARIs, such as finasteride and dutasteride, are frequently used to treat lower urinary tract symptoms associated with benign prostatic hypertrophy and androgenic alopecia. They have potential as chemopreventive agents.