“Everything looks good” doesn’t tell enough. If there’s no cancer, the report should say something like “benign,” or “no tumor present,” or something like that. You should ask specifics about the biopsy results. That will help track any progression going forward.

If “1 out of 10” samples was cancerous, they would have given that one sample a Gleason score. (In the biopsy report, what was the exact wording about that one sample?)

If there’s no cancer, then there’s nothing to treat or risk to spread.
> What is his PSA?
> What led to him getting an MRI and a biopsy?)

Treatments are always guided by the numbers:
> Total PSA; % Free PSA;
> PSA Doubling Time; PSA Density
> MRI results; biopsy results
> PSMA PET scan results
> genomic and genetic tests
> other diagnostic tests as needed

Is there a history of prostate cancer in his family?

The side-effects from treatment can be severe. If he has no symptoms and has no numbers indicating concern for cancer, I would simply keep tracking PSA regularly.

(I was 56y when I was diagnosed with PC; it was localized, 3+3=6, no other issues. I chose active surveillance; was on active surveillance for about 9 years. Then had proton radiation treatments when my PSA continued to rise and Gleason went to 7. My wife panicked when she heard about the 3+3=6; said she couldn’t stand the thought of cancer being in my body. But, I showed her the data that a true Gleason 6 doesn’t metastasize, and that active surveillance would allow me to wait and catch it early, and if it wasn’t a “true” Gleason 6, to still treat it. Here I am now, 13+ years later and it’s as if nothing ever happened. Our lives are completely normal. The first thing to control regarding prostate cancer are dark thoughts.)

Good luck!