Propecia and Prostate Cancer

Propecia label up close on a table

Ryan / Wikimedia Commons / CC BY 2.0

The hair-loss drug Propecia (finasteride) may significantly reduce the risk of prostate cancer, but the research on risks versus benefits is conflicting.

Used to treat male pattern baldness, enlarged prostate, and prostate cancer, Propecia blocks the activity of an enzyme called 5-alpha reductase. This enzyme converts the hormone testosterone into dihydrotestosterone, which is the most potent androgen in the prostate and plays a role in the development of prostate cancer. 

A 2003 paper published in the New England Journal of Medicine found Propecia, also sold under the brand name Proscar, reduced overall prostate cancer risk, but also significantly increased odds of being diagnosed with a more aggressive form of the disease. Since then, numerous follow-up studies have shown differing results.


In the Prostate Cancer Prevention Trial, 18,000 men aged 55 years and older were given either 5mg finasteride daily or a placebo. After seven years, those taking the medication had a 25% reduced likelihood of developing prostate cancer. However, the data also showed a 68% higher risk of being diagnosed with a later stage of prostate cancer. The study authors concluded that while finasteride may prevent the disease, it also may delay the detection of prostate cancer. 

Further research suggests the risk of delayed detection is much lower than previously thought. A 2019 long-term analysis of the trial found no increased risk exists. In addition, the 18-year follow-up found men in the finasteride group had a 25% lower risk of death by prostate cancer than those who took a placebo. 

What's more, a 2018 follow-up study found Propecia’s benefits lasted long after men stopped taking the drug. Researchers used Medicare claims to follow the original study participants and found after an average of 16 years, men in the finasteride group had at 21% reduced risk of prostate cancer diagnosis, even after they ceased the medication. 

While the latest research suggests the benefits outweigh the risks, the decision to take Propecia to prevent prostate cancer should be made between you and your doctor, based on your family history of the disease and other factors.

Other Uses

Propecia inhibits the conversion of testosterone into dihydrotestosterone and is used for more than just a cancer-preventive agent. Additional uses include:

  • Enlarged prostate
  • Scalp hair loss in men
  • Excessive body hair in women, known as hirsutism, which is common in women with polycystic ovary syndrome (PCOS)
  • Transgender hormone therapy along with estrogen for male-to-female transitions

Side Effects

Since Propecia alters testosterone levels, sexual side effects can occur and may be troubling for men. In fact, one study found that one-third of patients stop using the drug due to sexual side effects. These include:

  • Decreased sex drive
  • Trouble getting or keeping an erection
  • Ejaculation disorder

Propecia may also affect breast tissue in both men and women, including an increase in breast size and breast tenderness. See your doctor if you experience lumps or pain in your breast or nipple discharge.

Skin rash and depression have also been reported as side effects of Propecia. Allergic reactions may occur and have serious or life-threatening effects, including anaphylaxis. Call 911 if you have difficulty breathing or swelling of your lips, tongue, throat, or face.

A Word From Verywell

Like all medications, Propecia has benefits and risks. If you are interested in taking Propecia in the hopes of prostate cancer prevention, talk to your doctor and your insurance provider. Many policies cover generic finasteride but not brand names Propecia or Proscar.

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Article Sources

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  1. Thompson IM, Goodman PJ, Tangen CM, et al. The influence of finasteride on the development of prostate cancer. N Engl J Med. 2003;349(3):215-24. doi:10.1056/NEJMoa030660

  2. Goodman PJ, Tangen CM, Darke AK, et al. Long-term effects of finasteride on prostate cancer mortalityN Engl J Med. 2019;380(4):393–394. doi:10.1056/NEJMc1809961

  3. Unger JM, Hershman DL, Till C, et al. Using Medicare Claims to Examine Long-term Prostate Cancer Risk of Finasteride in the Prostate Cancer Prevention Trial. J Natl Cancer Inst. 2018;110(11):1208-1215. doi:10.1093/jnci/djy035

  4. National Cancer Institute. Prostate Cancer Prevention – for health professionals (PDQ)

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