Husband's PSA is now .18 post RP 8.5 years ago

My husband Paul is now 71.5 years old and had a regular RP 8.5 years ago and the doctor said the pathology reports said the cancer had penetrated his urethra, but that is was possible since it was on the border all it may have been cut out due to where he had to cut. For the past 8.5 years, Paul's PSA tests have come back non-detectable. Then four months ago, his PSA came back .18, and now four months later, it is still .18. Doctor said there may be some cancer there or the .18 could be caused from something else. Went on to say that since it had been non-detectable all these years until four months ago and did not go up any higher four months later now, he took that as a good sign, yet seems confused and baffled about it. He brought up the subject of radiation saying Paul may benefit from it and if he wanted to get it he would not be against it. He sounds like he leans towards it yet he wants it to be Paul's idea to do it because he does not come out and say I recommend you have radiation.
He is a very reputable well established urologist and considered to be one of the very best, so go figure.

We had thought after all these years of good PSA's we stood a strong chance of being out of the woods and now we almost feel like we did 8.5 years ago when Paul was first diagnosed. We do not want to waste valuable time and do nothing if there is any chance this could shorten his life.

There are other concerns as Paul is a type II diabetic which is managed well without meds now, is a stroke survivor, and is on Plavix. Not sure how he would do with radiation or if he may effect his quality of life with permanent side effects if there were any damages to his bladder or/colon.

So many questions running through our heads on what we should do or should not do and if or when. Any input would be greatly appreciated.

Julie