Did you try anything on your dog's tumor, like "Two Feathers" Native American Salve? It draws out tumors. The founder, Mr. Roy, talks you through everything about how to use it. You would have to cover it with a bandage, so the dog doesn't lick it off. Many things draw tumors out. Castor Oil packs, even Urine can help a lot. Kidney herbs, like Andreas Moritz 's Kidney recipe, can help the kidney clear the tumor at the same time the salve is working. Just an idea. I have heard many people using such natural remedies on their dogs and the dogs recover beautifully.
I like Andreas Moritz 's books a lot. He talks a lot about ayurveda. Anytime I stray from my proper ayurvedic diet for my dosha "Pitta" (Fire), I feel so sick. All his tips are so simple, yet very very effective.