Myth or Fact: Can Finasteride Cause Prostate Cancer?

Written by Malavika Varma, MD

Finasteride, an anti-androgenic medication is an oral tablet used to treat male pattern hair loss. It slows down the process of hair loss by inhibiting the formation of excess androgens. Studies have proven that finasteride 1mg meaningfully improves hair count, hair thickness, colour, and length for people who use it regularly.

Is it Linked with Prostate Cancer?

The answer, according to the latest studies as of 2018, is no. In fact, finasteride reduces the risk of getting a low-grade prostate cancer. One study did show it may cause a more aggressive form of prostate cancer if you were to get it, but later studies have shown the numbers behind this are not statistically significant.

The authoritative source for this conclusion is the Prostate Cancer Prevention Trial (PCPT) conducted in 1993 with follow up studies in 2013 and 2018. It was a randomized clinical trial designed to see whether the drug finasteride (5mg) could prevent prostate cancer in men aged 55 and older. The participants were in good health and did not show any symptoms or signs of prostate cancer. The trial was placebo controlled. Participants who didn’t get finasteride got a dummy pill. None of the patients knew whether they were taking real finasteride or a dummy pill.

Patients were monitored yearly via digital rectal examination (DRE) and Prostate Specific Antigen (PSA) level — a blood test used to screen for prostate cancer. If abnormal findings were felt or seen, a prostate biopsy was recommended to check for cancer during the trial. At the end of the seven year study, prostate biopsy was also recommended for patients who were not diagnosed with prostate cancer during the trial to assess their prostate health.

In 2003, NEJM (The New England Journal of Medicine) published the results of this trial. The study found that finasteride reduced the risk of prostate cancer by 25% but was associated with a slight increase in high-grade (more aggressive) disease among men in the finasteride group (6.4%) versus men in the placebo group (5.1%). The absolute increase was only 1.3%.

In 2013, with more follow-up, the risk of developing prostate cancer remained lower in the patients who had received finasteride – by about 30%  (10.5% of men in the finasteride group versus 14.9% of men in the placebo group were diagnosed with prostate cancer). This difference in prostate cancer diagnosis was entirely due to fewer low-grade prostate cancers in the finasteride group. Although the slight increase in high-grade disease continued in the finasteride group (3.5%) versus the placebo group (3%), this difference was no longer statistically significant – meaning that it could simply be due to chance.

Similarly in a recent follow-up study in 2018, which followed the patients in PCPT for about 18 years, it was shown that finasteride indeed reduced the risk of prostate cancer by about one-third. There was no significant difference between those who received finasteride versus those who just received placebo in terms of overall survival or survival after the diagnosis of prostate cancer.

The Bottom Line

So at the end of the day, what does all this mean for patients taking finasteride? Well for those men taking 5mg of finasteride, there seems to be a lower risk of prostate cancer overall. However, only the risk of treatable low grade prostate cancer is reduced. Patients taking finasteride likely won't live any longer than patients who don't since the cancers prevented are less aggressive.

Whereas patients taking finasteride in the clinical trial who ended up with prostate cancer tended to have more aggressive disease, the recent long-term follow up results imply that taking finasteride did not put patients at risk of dying early. They also imply that the difference in the number of patients with more aggressive prostate cancer could be simply due to chance.

It is also worth keeping in mind that the dose used in these trials is 5mg of finasteride whereas the dose used for male pattern hair loss is 1mg, meaning that conclusions brought up by these studies might be minimized even further for men taking finasteride for hair loss.

This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for and should never be relied upon for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment.