Hi , sorry you are here.
You don't say how old your dad is or how active he is so I may not be comparing apples with apples but I was diagnosed with advanced prostate cancer in November 2014 age 49.
Once I got over a couple of months emotional denial I decided to push myself and make the most of it. I came to the conclusion that no matter how justified, a day feeling sad was a wasted day.
I turned my energy into running, raising money for Prostate Cancer UK ( the charity whose forum we use and benefit greatly from), spreading awareness and trying to let people understand just how important living for the day is , cancer or no cancer.
I ran two marathons on chemotherapy, have completed the marathon des sables (250k across the Sahara)twice plus a bunch of similar races and in 5 weeks am off to the arctic for a 380 mile race unsupported pulling a sledge, it will be -50c or more at times ( then back to do the MDS, +50c, for a third time 2 weeks later).
So whilst everyone does not have the ability to do what I do, it is possible to do so much even with advanced prostate cancer, I never ran that far before I had cancer.
You will of course know more when you get dads results but before and after that don't let a preconception of prostate cancer stop your dad doing anything.