I was told it by my key worker ie the designated contact person for prostate patients such as me at the NHS hospital concerned.
She didn't know any reasoning behind it but said that the hospital's focal therapy team (it does have one, I gather) must have considered my case unsuitable for focal therapy, otherwise the wider multidisciplinary team wouldn't have assigned me to a choice between:
a. robotic prostatectomy surgery, or:
b. external beam radiotherapy, preceded and followed by months of hormone treatment.
I've since had phone calls from one of their surgeons & one of their oncologists. They advocated options A and B respectively, and said the choice between the 2 was up to me. Neither mentioned focal therapy till I asked. The surgeon then said the focal team didn't regard my prostate as suitable, with its median lobe getting in the way of the ultrasound ( or words to that effect). He added that this median/middle part would also complicate the bladder neck reconstruction required to complete prostatectomy ( if I choose the surgery option - though he was optimistic overall).
The oncologist took the same line about it being an issue for the focal team who either had said no or would say no. I pressed him on whether I could actually talk to the focal team to get more of an explanation. He said he would pass my request on to them. He added that focal therapy was not a standard care pathway, unlike both surgery and radiotherapy/hormone.