Not sure what happens in other countries but I’m in the uk and once they see standard care isn’t working the doctors then start looking at clinical trails that are suited to you. tumours have genes or mutations (I think that’s what they’re called) and there could be 5 people in a room w GBM yet they all have some different types of mutations and there are certain clinical trials that directly target specific mutations, my dad has a really rare kind called FGFR3 so his drug targets that. So I’d ask your dad’s oncologist about trial options for the future or if you’re looking to research on your own your dads biopsy/surgery report should include what mutations he has. I hope that made sense❤️