According to researchers at the University of Washington School of Medicine, men who develop early onset male pattern baldness had a significant reduction in the risk of prostate cancer. The researchers studied 2000 men aged 40 to 47.

“At first, the findings were surprising,” said professor Jonathan Wright of the University of Washington School of Medicine in Seattle. “But we found that early onset baldness was associated with a 29 percent to 45 percent reduction in their relative risk of prostate cancer.”
Helen Rippon, head of research management at The Prostate Cancer Charity, added: “If these results are correct, they could be useful in providing us with a greater understanding of how testosterone behaves in the body and how it can affect different tissues.”

I thought it was opposite - the ppl i know who had prostate cancer are quite bald

Maybe the key is "early onset baldness".

Proscar is the 5x dose of Propecia.

Proscar is used to reduce DHT to reduce the size of the prostate. Propecia is tha same medication in a smaller quantity that is used to reduce DHT in order to regrow hair.

Maybe it has to do with WHEN your body is producing an excess amount of DHT? I believe prostate issues are more common in the 35-40+ demographic, if I'm not mistaken.