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.
age 67 PSA 5.8 DRE slightly firm Rt
Biopsy 2nd July 07 5 out of 12 positive
Gleason 3+4=7 right side tumour adenocarcinoma stage T2a
RP on 30th July,
Post op Pathology, tumour stage T3a 4+3=7, microcsopic evidence of capsular penetration, seminal vessels, bladder neck, free of tumour, lymph nodes clear, no evidence of metastatic malignancy, tumour does not extend to the apical margins.
Post op PSA 0.5 26th Sept.
PSA 23rd Oct.0.5 seeing Radiation Onocologist 31st Oct.
Started radiation treatment on 5th Dec, to continue until 24 Jan. 08.
Finished treatment, next PSA on 30th April.