Have you considered Protocel? Tanya Harter Pierce cites at least one case history (Outsmart Your Cancer) involving a pet - pretty sure it was a dog, but I'll check.
Of all the organs, the liver has arguably the greatest recuperative/regenerative powers, so there's hope for your dog. The Protocel route would also save your dog an op., as the tumor undergoes apoptosis, then removal thru the 'waste disposal system'. Worth investigating, I would have thought.