One possibility would be for him to go on to hormone therapy. That will shrink the prostate and may alleviate the enlarged prostate symptoms, in addition to stopping the cancer for now. He could try it and see how he gets on.
He could even try just Bicalutamide alone (a hormone therapy which has fewer side effects, and strengthens rather than weakens bones). It typically works for up to a couple of years. If he came off it at that point and it had been successful, he could either switch to Finasteride to maintain the smaller prostate, or switch to hormone therapy injections.