Homeopathy
Homeopathy is a very interesting field that uses the principle "like cures like." In the Dog Cancer Survival Guide, Dr. Dressler states that homeopathy has been shown to be useful in certain types of human brain cancer, and potentially other forms of cancer, in conjunction with medications.
You should consult with a veterinarian trained in homeopathy if you are interested in trying it.
You can find a homeopath in your area by going online to this site: American Holistic Veterinary Medical Association