Hi mjr, I completed radiation therapy on 24th Jan. had a chat to my urologist today because I was impatient to find out my PSA ( which is scheduled for 30th April ) he said they always wait 3 months, as the radiation aggravates target area, and the early PSA is not conclusive, in my case, he said he fully expects the PSA to be .0..........so here's hoping. 
Regards Mal.