I'm sorry, man. We lost ours to cancer in June. It's a terrible thing.
But with a tremendous amount of care from his oncologist, we were able to keep him alive for over a year and a half with a pretty good quality of life for most of it. So don't give up hope. They can treat canine cancer very well nowadays, and can prescribe a lot of drugs, even ones like Marinol, to keep him happy and comfortable for a while.
Feel free to reach out if you need advice or support.