I researched Cryotherapy and Cyberknife (which I think is similar to Nanoknife?) back in 2013 when my initial (2009) external beam radiotherapy was deemed to have failed.
My original consultant, coincidentally was the local Cryotherapy expert having conducted trials, he told me in no uncertain terms that I wasn't suitable for cryotherapy. I might be totally wrong here, but I got the impression that cryotherapy was a viable option for patients with small tumours located within the prostate gland. But for large tumours, or those near the edge of the gland, cryotherapy caused problems to surrounding tissues. The problem seems to be keeping surrounding tissue warm enough to remain viable, whilst freezing the adjacent tumour enough to kill it off.
I know another patient who had salvage cryotherapy and ended up having to have reconstruction work on his bladder where the cryotherapy had 'burned' or 'frozen' if you prefer, a hole in his bladder.
In my case I was referred to another consultant at a different hospital where I was offered HDR Brachytherapy, and that seems to have done the trick, in that currently my PSA is well within expectations.
To my way of thinking, the beauty of HDR Brachytherapy is that they insert the tubes, then scan you so they can see that the tubes are in exactly the right place, then once they are satisfied, they insert the radioactive rods and cook the tumour from the inside. Whereas with any external beam method, you have to do your best to keep still, and every time you cough or twitch you are causing the beams to miss their target.