Hi Skiingbuffy,
I first saw a TV documentary about 5 years ago which featured Cyberknife, it can be used for the treatment of many types of cancer, and its big appeal for PCa was that it could be used as a salvage treatment for PCa patients who had previously had EBRT.
I did a bit of research in 2013-14, at that time one of the London hospitals and the QE2 at Birmingham had Cyberknife.
Armed with this info I asked my consultant if I could have it and he referred me instead to Mount Vernon for HDR Brachytherapy, which was the latest development, matching if not superseding Cyberknife.
From a layman's perspective I think the Doctor's can kill off any cancer with RT, but the problem is that if they are not careful they will kill off surrounding tissue as well, so its a sort of Goldilocks problem, not too little, and not too much, because they want you to be left with a functioning bowel and bladder after treatment.
The beauty of Cyberkife is that it shoots the radiation in from so many angles, that it minimises collateral damage to surrounding tissue, however so does HDR brachytherapy, because they push the radioactive rods into the tumour and cook it from the inside out.
My local support group spends much of it's time raising funds to buy new kit for our hospital, when we asked them what they wanted they said HDR brachytherapy kit, so if that is what you are being offered there might be good reason for it.
:)
Dave