Finasteride and Prostate Cancer

Finasteride (also known as Proscar or Propecia) is a well-known androgen blocker used to treat hair loss in men and issues with an enlarged prostate. It blocks the conversion of testosterone into its more potent form, dihydrotestosterone (DHT), known to promote prostate cancer growth and progression. For those being treated for an enlarged prostate, finasteride decreased prostate-specific antigen (PSA) levels by up to 50%. Furthermore, limiting the influence of androgens on the prostate is a common go-to strategy to treat advanced prostate cancer. Researchers then asked the question – why not reuse this drug to treat prostate cancer?

Specially designed to mimic testosterone, finasteride binds to the enzyme 5-alpha-reductase, which converts testosterone into the more potent DHT. By taking the place of testosterone molecules, it prevents them from being able to be converted to DHT. This helps to limit the DHT in your body, preventing further growth of the prostate and limiting hair loss.

Through the Prostate Cancer Prevention Trial in 2003, it was found that finasteride taken over 7 years managed to reduce low-grade prostate cancer risk by almost 25% in those 55 or older. In a follow-up study 16 years later, it was also found its benefits lasted long after the original treatment. However, the risk of higher-grade cancer (Gleason score ranging from 7 to 10) increased after taking finasteride. This ultimately stunted the adoption of finasteride as a prostate cancer treatment, as it led to many recommendations against using it.

While quite a few studies have been conducted, their results remain conflicting and the use of finasteride to treat prostate cancer still remains controversial. Ultimately, the drug remains unapproved by the US Food and Drug Administration for prostate cancer. However, it is still approved to treat hair loss in males, or those with an enlarged prostate.

If you are taking finasteride for hair loss or an enlarged prostate, your PSA levels should be monitored carefully, as finasteride can reduce PSA levels even in the presence of prostate cancer. There may be a risk of false negative results during regular prostate cancer screening, with some recommendations to double the PSA test results when comparing them to established prostate cancer reference ranges.