I had one 4 months after surgery, but my internist didn't want to do it unless prostate surgeon said ok. Surgeon said no problem, just be careful as the tissue between prostate bed and recturm is now thinner than it use to be, but it would be no problem, and as was mentioned above, just let your internist know your history. And the test is a breeze.
They did find some small polyps which they took care of with the scope and thankfully they were not cancerous. Now because they found polyps, I have to get one every 3 years. My wife will have one soon.
Wish you the best, when your health and life is concerned, there are no dumb questions.