I ran into the following article which shows the general direction for exploring the prevention of prostate cancer. The following is the introduction to the the journal article.
INTRODUCTION: If an agent can slow the growth of existing prostate cancer cells, it remains plausible that it may be effective as an adjunct to surgery, radiation or chemotherapy.
DISCUSSION: Level-1 evidence will be needed in order to definitively prove the efficacy of agents as chemoprevention strategies for prostate cancer. Currently, only finasteride fulfills this criterion. Two major trials are underway that will assess the role of soy, vitamin E and selenium in prostate cancer prevention.
CONCLUSION: Tantalizing prospects for effective chemoprevention of prostate cancer exist. Fortunately, well-conducted randomized trials will allow us to answer many of these questions within the next 2 to 8 years.
Source: Can J Urol. 2005 Jun;12(3 Suppl):2-4. Prostate cancer: chemoprevention update 2005 by: Fleshner N, Al Azab R. Department of Surgery (Urology), University Health Network and University of Toronto, Toronto, Ontario, Canada.
Please note that Finasteride (Propecia/Proscar) is presently the only agent for prevention of prostate cancer so its use in hair loss has clear benefits beyond the ability of the drug to reduce the rate of or possibly reverse the hair loss.