Sounds like he is in my part of the court.
My suggestion is to read up on the subject, not so much that you can offer help as to just understand the lay of the land, as it were.
The good books, and a long list of things to do / ask about are in the top 4 threads of this forum (so-called "sticky" because they stay at the top).
I'll suggest some books that you might find at a local library. If you have a local Prostate Cancer foundation, ask for help there. If not, go on line and look for USToo.org, which is a national organization that has local support groups. Yes, you can go to a support group meeting. They are for the newly-diagnosed, survivors, and those who have to put up with us.
A good lightweight "covers most of it from 10,000 feet" book would be The Cleveland Clinic Guide to Prostate Cancer (Eric Klein, MD 2009).
The heavy-duty "in the trenches" guidebook is Guide to Surviving Prostate Cancer (2nd ed.) (Patrick Walsh, MD, 2007).
There are others, and in fact a simple one that you can download free as a PDF is available from Australia. It is directed at a different audience, but has a section on treatments and side effects that is concise. I'll get the link and come back to put it in this post in a few minutes.
I hate it that you have to visit us, but you are welcome. Ask questions as needed. We've got a pretty good spread of experience we wish we didn't have -
Here is the link:
Go to the bottom of the page, were you will find a link to download a free pdf copy. I have downloaded this and did not find any security issues.
The book is an argument about general testing, but it has some good general info. Some of the statistics are based on Australia, so don't match the US experience. Read around those points.