Many anti-cancer drugs are toxic to normal cells as well as cancer cells and can have toxic side effects. For this reason, scientists must test them on higher-order animals, such as dogs, ferrets, or rabbits, before human beings take the new drug or before drugs can be administered to pets, livestock, etc. If the drug may cause a particular side effect in humans, the researcher picks an animal species to best model that possible side effect. In these tests, scientists use the fewest animals possible and minimize the animals' discomfort. Some tests for new cancer treatments and diagnostic techniques are performed on veterinary patients.
Veterinarians conduct clinical trials using people's sick pets, with the owners' permission.
These tests often provide beneficial new cancer treatments for animals that may ultimately be used for humans. Veterinary patients often benefit from new cancer drugs two to five years before humans, because new drugs can go into clinical trials for animals at a faster pace than for humans.