I stand ready to be corrected on this because my medical knowledge is mediocre, gained by experience at the sharp end.
I wouldn't get too wound up about the PSA number. As you know, the important thing is going to be whether there's been a metastasis form the prostatic capsule.
I should have thought that his urologist would do CT scan of the prostate, a lung X ray and a nuclear bone scan,
His urologist might well take a biopsy sample, perhaps a transperineal or targeted biopsy rather than the cruder anal biopsy. This will produce the well known Gleason score.
All of these results will be put into the melting pot and a determination as to treatment will be made depending on the likelihood or actually determinable escape of not of cancer cells from the prostatic capsule.
Good luck to your brother in law. It's all a most terrifying journey he's embarking on.