I understand you are concerned. Anyone would be. Could you please share what treatments your husband received upon his stage 4 diagnosis? Did he get any radiation? Did he have Chemo? Is he healthy enough for chemo? Typically what the doctors may do is schedule a PMSA Pet scan. It will light up the areas where the cancer is growing. Hopefully, it is confined to one specific area. If it is, they may suggested targeted radiation on the specific area where the cancer is growing. If the PSMA Pet scan shows several spots more spread out, they may suggest a treatment that is considered more Systemic. Those treatments may include chemo such as Docetaxil and or Carboplatin. Or they may suggested Pluvicto and or Radium 223 if the spots are limited to bone. Regardless, you should immediately request genetic and genomic testing. Genomic testing is a blood test that will show if there are any genetic markers such as BRC1, BRC2 that your doctor can act on with treatments. That is important because there are treatments that target those genetic mutations specifically. And yes, if you can, ask your doctor to switch to Nubeqa (Darolutamide). It is a wonder drug for many. Some doctor believe that once Resistance starts switching your ARSI does not work. I am not so sure about that. Xgeva is specifically for bone strength and is used to help prevent the bone loss from being on long term ADT treatment. Praying that you get the best treatment in your situation. Also Praying for you and your husband.