You are running into a problem many of us are worried about having. We’re waiting for the next possible drug that can treat people when the ARPI‘s fail (enzalutamide, etc).

If the new metastasis are strictly to the bone, then radium 223 (Xofigo) is an option that can be considered.

The only other option at this point is chemotherapy. Has this been discussed with your doctor? You say he can’t tolerate it, but it may be the only choice.

I know someone who went to Austria to get actinium, It is available in the United States, but it is hard to find since it is only under a clinical trial. It might make a difference, I know people who have had a second Lu-177 Set of treatments, Insurance paid for it because they were the first one under the clinical trials. It is being done in some foreign countries as well. The problem is, it doesn’t have a high percentage of success for the long-term, I would think since it failed so quickly they might not consider it.