Elena,
My first thought follows the first question Lyn raised. What was your Dads PSA when first Diagnosed? What was it just prior to treatment and when the RT was administered and when was that? Has it now increased (perhaps after the lowest point after treatment called 'nadir') to a level or in a way that indicates that the RT was not successful? It has to be remembered that RT goes on working for something like two years but if Hormone Treatment was also given, this would usually help drop the PSA for the period it was given and for a relatively short time afterwards, after which the RT would be acting on it's own.
If indeed he was given inadequate RT (and not just the alternative of fewer fractions of a higher dose), has he asked whether further RT could be given now, perhaps together with HT? Maybe he would not wish to go this route after his previous experience even if offered? A relatively small number of men have surgery after RT due to only few surgeons being prepared to do this and the increased risk of more severe side effects.
There are other treatments for where the cancer is contained within the Prostate. Two of these are HIFU (High Intensity Focal Ultrasound) and Cryotherapy and they can be given where RT has failed. However, these are only available in a few countries and mostly would have to be paid for by the patient or his insurers where not provided as a state service.