@BShark Every case is different, and listen to the doctors, but your “cure is as bad as the disease” comment made me remember one of my uncles. He suffered with prostrate cancer and went through all the procedures - chemo, radiation, etc. When he was on death’s doorstep he said no more “treatment”. He lived another relatively good 12 years.
If you’re inclined, you’re already praying. If not, a bunch of us are praying for you, for your brother. Hang in there.