grandpa with gbm admitted again

my grandpa was admitted again last Wednesday for seizure like symptoms and lost his ability to talk right after his episode but now it's been almost a week and he's been laying in the hospital for so long and has been sleeping for so much of it because they've put him on 3 anti seizure medications. doctor told me to consider the original prognosis of 12-15 months because he's been diagnosed for a year now.

he's now unable to move his right arm and leg and can barely say a full sentence and can't stay awake for more than a couple minutes and also now has a feeding tub inserted through his nose.

I don't understand because his tumor hasn't grown much since his surgery in March last year but now he's gotten significantly worse just within a few months but his oncologist was saying how he was stable and were planning on starting optune.

sorry this has been such a ramble I'm just lost because I've been translating for my family and trying to understand why this is happening anybody else have had this happen where conditions just suddenly progress like this?