Going through the same with my dobie gal. Same spot. Vet says too massive to remove and very close to the lung.
We opted to give her a good quality of life and when it is time, we will do what needs to be done. So far, she is doing great and thankfully she has no idea that she is terminal. So we just treat her like the rest of the gang and do give her those little extras on the side.
I am so sorry you are going through this. Celebrate each day even when they are not ill. Just makes things feel alittle more normal.
Good vibes coming your way.