Dear Richard,

Physicians do not trump the moral law, and masturbation is a sinful act, that doesn't change because a doctor says so.  Your body is going to die, but your soul will go on forever.  

Materialism (in practical terms, the societal ethos) puts the emphasis on caring for the body, which is temporal, to the detriment of the soul.  Don't invert the priority of which element is most important; care for your soul above all; you will get a new body in the end anyway (We believe in the Resurrection of the body!).  God rewards us for doing the right thing, especially when sacrifice is involved.

If you are concerned about your prostate, there are supplements that can help without resorting to immoral acts.  Do some research and you'll find them.  

Consider how every celibate priest or monk, saint or celibate follower of Christ has fared; they survived without sex acts, and you will too.

Peace,