New Health Canada Warnings about Finasteride, Dutasteride and Prostate Cancer


Prostate cancer is one of the most commonly diagnosed cancers in men. In fact, about one in six men will be diagnosed with prostate cancer. One new case of prostate cancer occurs every 2.2 minutes and a man dies from prostate cancer every 15.6 minutes.

Health Canada released a statement last week about the possible increased risk of “high-grade” (aggressive) prostate cancer in men taking the drugs finasteride and dutasteride.  Both of these drugs are used to treat male balding but are also used to treat men with enlarged prostate glands. Large numbers of my patients have asked me about the Health Canada statement in the past weeks –  Click on the link to read more about the Health Canada statement.



In order to understand the meaning of the Health Canada warning about finasteride and dutasteride, it’s important to have some background information.  First, it’s important to know that there were TWO very large studies conducted a few years ago (one in 2003 and one in 2008) looking at whether finasteride and dutasteride could actually help prevent prostate cancer in men. 

The two reserach studies are:


STUDY 1: Prostate Cancer Prevention Trial (or ‘PCPT’ Trial)

  • This was a 2003 study of 18,000 men over 55 years of age
  • This study showed finasteride reduced the risk of men getting prostate cancer by 25 %
  • There was a slight increased in high grade (more aggressive) prostate cancers in men who took the drug compared to those who took the placebo (sugar pill)
  • The dose of finasteride in this study was  five times higher dose of finsasteride than used for hair loss (i.e. 5 mg rather than 1 mg)


STUDY 2: Reduction by Dutasteride of  Prostate Cancer Events (or REDUCE Trial)

  • This was a study in 2008 of over 6700 men age 50 to 75
  • Over the 4 years of the study, there as a 23 % reduction in prostate cancer in men who took the drug
  • There was a slight increase in high grade (more aggressive) prostate cancers  in year 3 and 4 in men who received the drug compared to men who received the placebo (sugar pill) but overall the raw data showed there was no increase risk of high grade cancers throughout all years of the study.
  • The dose of dutasteride was the same as used for hair loss (i.e. 0.5 mg)



  • The data from these two studies is complicated to interpret
  • There is no question whatsoever that finasteride and dutasteride both reduce the risk of men getting prostate cancer.
  • What is not entirely clear is if these two drugs increase the chance of men getting a "high grade" cancer.  It’s possible that for every four low-grade (non aggressive cancers) that these drugs prevent, there is one high grade cancer that gets detected while on the drug.

But do these drugs make it "easier" to detect a cancer that would have otherwise escaped detection?


Do these drugs actually contribute to the development of the prostate cancer?


The answer to these questions is not known with complete certainly.  There are several explanations as to why more high grade prostate cancers were detected in men who took the drug.  For the most part, most authorities in prostate cancer do not believe there is a cause for alarm. In fact, the number of world authorities on prostate cancer who believes there could be a link between finasteride and prostate cancer is greatly outnumber by authorities who feel there is no link whatsover.  This includes Dr Otis Brawley, Chief Medical Officer of the American Cancer Society and Dr Neil Flesher, Head Division of Urology at the University Health Network and Professor of Surgery at the University of Toronto. The public needs to know this information is not cut and dry.



  • If there is any risk of high grade prostate cancer with these drugs (again, we can't say for sure there even is).... the risk is very small.
  • The public should be aware that the new Health Canada warnings do not state that finasteride or dutateride causes high grade prostate cancer. Rather, the warning states that there could be a link and more studies are needed.
  • The studies discussed above were conducted with five times higher dose of finsasteride than used for hair loss (i.e. 5 mg rather than 1 mg).  Therefore, Propecia (finasteride 1 mg) was not included in these studies
  • The dose of dutasteride in these studies was the same as used for hair loss (0.5 mg)
  • Individuals with concerns about these drugs should speak to their doctors






Dr. Jeff Donovan is a Canadian and US board certified dermatologist specializing exclusively in hair loss. To schedule a consultation, please call the Whistler office at 604.283.1887

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