Here is an interesting article in the Globe and Mail about how treating naturally occurring cancer in animals may help to understand treatment for humans as well.
Researchers have traditionally used lab rats and mice with artificially induced tumours to develop and test new cancer treatments, says Dr. Coomber, whose research focuses on tumour biology. Pets, on the other hand, arrive at veterinary clinics as patients. Their tumours occur naturally, just like in humans. Some tumours in companion animals - dogs in particular - behave similarly to tumours in humans.