Dear Best Friend:
If your friend was older then, with his stats, doing nothing (watchful waiting) might be a good option. However, at his age, that is not a good idea in my opinion.
And, your urologist is incorrect when he states that ALL PCa treatments result in total loss of ejaculate. I suggest you look on this forum at the threads started by realziggy. He successfully underwent targeted focal therapy, which is akin to lumpectomy for breast cancer. In that treatment, the patient undergoes an extensive biopsy, then needles are inserted into the prostate to destroy the cancer only...not the entire prostate. Ziggy was perfectly clear that he retained his ejaculate.
Beyond that, brachytherapy results in loss of some or all ejaculate. I can't seem to finds stats on what percentage of patients retain some and what percent lose all. But, my radiation oncologist told me there was a "decent chance" that I would retain some ejaculate in the long term. 6 months out I have reduced ejaculate and I can't tell the difference between before and after...but, it's still early for me and I may yet lose it all. JustJulie on this forum has a longer term view with her hubby and she may weign in with their personal experience. Also, this whole thing with brachytherapy may be age and case dependent, as is the situation with lots of this PCa stuff. Somewhere along the line your friend should speak to a radiation oncologist anyway, so this question should be posed to him/her.