Proton therapy...which we couldn’t even have imagined not too long ago.
But I know he is suffering, and do so pray for his quick relief, as well as yours. It’s so easy to say but, be strong.
I had that treatment at Loma Linda about 4 years ago, for an acoustic neuroma. Seems to have worked, of course I am practically brain dead but alive :)
Prayers up for your dad, may He bless and keep you always.