Contrary to some of the posts I've read here, most of the studies I've read show that resistance aerobic exercise (bicycling in particular) have shown to not only slow growth, but actually shrink enlarged prostates. Scientist don't know why it works yet, they suspect that it modifies hormone levels that signal tumor cells that it's time to kill themselves (apoptosis).

Of course there is a lot of crap info in the internet, but I would suggest those interested google bicycling exercise prostate and look at articles from google scholar or NIH or PLOS sites. There is a wealth of stuff to read on the subject.

For example
http://journals.plos.org/plosone/art...l.pone.0067579
Shows that exercise is really hard on tumor cells.