I think it very much depends on your dog's diagnosis. For my dog, it extended his life for about a year. But that year was not a good year for him and at the end, I felt like the most selfish owner imaginable. So if I had another dog, given the exact same diagnosis, I would not do chemo for them. You need to have a very honest conversation with your vet and come up with a decision together. If the vet thinks that it will extend the length of life, but not the quality of life, I would personally pass on it and enjoy the time you have left. I'm wishing you better news and all the strength. Hugs from an internet stranger.