Thanks for the responses, Wiosal, and Andy62.
It looks like my new PET scan is scheduled in about three weeks' time and I am to have another consultation with my oncologist shortly afterward to decide on a plan of action. My post-chemo MRI scan showed that the PC had shrunk 'considerably' both in the prostate and surrounding area which makes the most recent PSA test result puzzling. The latest was 1.25. My PC was initially diagnosed as aggressive - Gleason 9 - so I am more than half expecting the scan to show that the chemo and radiation did not get it all the last time around.