Finasteride: Does it Increase the Risk of Breast Cancer in Men?

Health Canada issued a news release August 4, 2011 advising doctors and the public of the possibility of breast cancer in men using the oral medication finasteride. Finasteride at 1 mg is used approved for the treatment of hereditary hair loss in men and is marketed under the name Propecia. Finasteride at a 5 mg dose is used for the treatment of enlarged prostate in men and is marketed under the name Proscar. Although the drug is sometimes prescribed off-label to treat women with androgenetic alopecia, it is not FDA approved for women.

Reports of a possible association between finasteride and male breast cancer are not new.  The possibility of this association was raised over 10 years ago.  There are now at least 50 previous reports in the medical literature about men who developed breast cancer while taking finasteride at the 5 mg dose. There are at least 3 reports in the literature of men who developed breast cancer taking the 1 mg dose. 

Overall, breast cancer in men is rare. 99 % of breast cancers are diagnosed in women and 1 % are diagnosed in men.  Each year about 2000 new cases of male breast cancer are diagnosed in the United States and 200 cases are diagnosed in Canada. 

The public needs to be aware that these studies do not prove that finasteride causes breast cancer in men. This relationship is not known at the present time and more research is needed.  However, it remains a possibility.    The Health Canada report states:

Based on the currently available evidence, it is not known with certainty whether finasteride can cause breast cancer, nor can this possibility be ruled out at this point in time.

All men starting finasteride should be aware of the possibility that reports of breast cancer have rarely occurred in men taking finasteride.  The risks in women are unknown at the present time. Health Canada has advised individuals who take finasteride to report changes in their breasts to their doctors. These changes would include:

• Enlargement of the breasts
• Lumps in the breasts
• Tenderness or pain in the breasts
• Discharge from the breasts

 The Health Canada report is found in the following link:

Finasteride (Propecia, Proscar): Potential rare risk of breast cancer in men