You might possibly be deemed suitable for HIFU (by HIFU practitioners) if tests and biopsy show significant cancer in one (max 2) local part of the prostate only, with no mets, no spread.
Some people on here have reported that they were oversold HIFU. But in my experience, the relevant London NHS hospital made no attempt to 'sell' it, they just agreed to do it when asked. Before that, when I was first offered only a choice between HT/RT and prostatectomy, I looked into paying for HIFU privately, and (with hindsight) some of the private providers were maybe overselling it somewhat.
I knew about the risk of recurrence in a different part of the prostate but comforted myself that HIFU can be repeated in that instance. I was keen to avoid the notorious side effects of prolonged hormone treatment (more or less compulsory with radiotherapy) and I didn't want to take the risk of (potentially prolonged) incontinence from prostatectomy.
In the event I had a different side effect after HIFU: acute urine retention at night. All that energy they put in, to kill the localised cancer, inflamed the prostate and nearby tissue. I had to have emergency recatheterisation. Fortunately this resolved in a few weeks. Tamsulosin didn't seem to help, but antinflammatories did.
So that was that. Except that, my PSA after HIFU was almost unchanged from the level of 7 which had got me investigated for PCa in the first place. I was told, let's see what the next PSA reading is in a few months' time. Time passed, next PSA was almost unchanged. I wanted to know why, and a further contrast MRI was commissioned. It appeared to be clear, in the sense of no active cancer anywhere in the prostate. But next reading a few months later, PSA was up slightly, rather than down. Why, I asked. A PSMA PET scan was ordered. Came back last month: prostate cancer in 2 pelvic lymph nodes. The focal urol team have therefore referred me to their Onco urol colleagues who've promptly put me on HT, before RT in due course.
Obviously I now regret having HIFU. I'm now in a much worse and more dangerous situation than if I'd started HT/RT over 18 months ago, at a time when the then PSMA PET scan showed no cancer in nodes.
There's another thread on here in which a reference is made to a trial of HIFU (not in UK) which was stopped for reasons of 'oncological safety'. I'm not sure exactly what is meant but it might be the cancer 'getting out'.