Breast Cancer and Finasteride

I am confused about the incidence rate of sexual side effects from finasteride. The common number quoted for Propecia (1 mg) is ~1.8%. Studies of Proscar/5 mg finasteride appear to report considerably higher rates of associated sexual dysfunction, e.g., Gormley et al. 1992, PLESS, Mondaini et al. 2007, etc. Are the SD effects that strongly dose dependent? Is this difference related to the age etc. of the treatment group for finasteride 5 mg? Could you comment?

Also, could comment on finasteride and breast cancer. The FDA finasteride info site notes two studies that show breast cancer cases in the experimental group but not the control (again, with 5 mg finasteride). This is concerning.

I am 30, with some recession of hairline (clearly progressed in my older (33) brother), and no vertex hair loss. Given the moderate effectiveness of finasteride on frontal balding, I am more concerned about side effects than I might be otherwise.

Thanks for your help!

Yes, side effects of finasteride are dose dependent.

Although breast cancer is primarily a disease of women, almost 1% of breast cancers occur in men. In 2007, it is estimated that 2,030 men in the U.S. will develop invasive breast cancer (source: eMedicineHealth.com). The study on finasteride 5mg showed that 4 of the 3047 men developed breast cancer. Another study on finasteride 5mg showed that 0 of the 3040 men developed breast cancer, but 2 men (taking a placebo “sugar pill”) developed breast cancer. This information is supplied with every Propecia bottle.

The relationship between breast cancer and finasteride is currently unknown. It is natural to have concerns and you need to have a good doctor who you trust to talk this out with, but over the Internet is not the relationship you need.