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In the maximum tolerated dose (MTD) test to induce cancer, animals are exposed to a test chemical in huge quantities, given as much as they can tolerate without dying. Their suffering is unremitting in these experiments, as many are literally poisoned to death, and the ones kept alive are chronically wounded and in immense pain, on the verge of dying. The MTD test ignores the differences between the animals’ full immersion and immediate cancer, and the slower, irregular development of human cancers. This test does not imitate how humans get cancer. Since the starting point of this test is inaccurate, any results obtained are also inaccurate, making this test invalid and wasteful.


Researchers have known for decades that they can not accurately replicate human cancer in animal subjects. A 1972 Lancet states:


"Since no animal tumor is closely related to a cancer in human beings, an agent that is active in the laboratory may well prove useless clinically... This is hardly surprising, in view of the vastly different biochemical make-up of the animal model and of the human tumor which responds" 1


In an effort to bridge the divide between man and mouse, scientists have genetically engineered the “oncomouse” to induce cancer in mice. They insert human cancer genes into embryonic mice, who then reproduce these genes. Another Frankenstein-like creation in an attempt to induce human cancer in a non-human, xenograft mice are invaded with cancer from human tumors. Both approaches have failed. Cancer genes and tumors behave very differently depending upon whose body they are in, making it impossible to obtain human data from mice or other animals.


Yet, researchers continue to rely on animal models of cancer, wasting time, money, and most importantly, lives.


In one series of experiments, unborn puppies were injected with cancerous brain cells. Some developed tumors, which were then removed. The cells from these tumors were then implanted into the puppies’ brains. The dogs who developed brain tumors suffered convulsions, blindness, labored breathing, the inability to walk, and difficulty eating. They were forced to undergo radiation and chemotherapy, which caused vomiting, diarrhea, and inflammation, until they "couldn’t take anymore." Out of the 471 dogs in this experiment, less than ten developed brain cancer, and only two were deemed “successful,” giving this project a failure rate of 95-98% but a yearly grant of more than $200,000. This cruel approach contributed nothing to the understanding or treatment of human brain cancer.


In a seven-year period, millions of animals suffered through more than 38,000 experiments to determine if radiation caused cancer, wasting hundreds of thousands of tax dollars and telling us nothing. We know from human-based research that radiation is carcinogenic to us.


One common use of animals in cancer research is carcinogenicity testing--in which animals are dosed with high levels of chemicals for years on end. Cancer rates are then assessed.


This testing is infamously inaccurate. In one study of 20 chemicals known to not cause cancer in humans, 19 tested positive in animals.2 Conversely, researchers for the drug company Pfizer found that only 7 of 19 compounds known to cause cancer in humans tested positive in animal tests.3 It was claimed that when studying carcinogenicity in animals, "we would have been better off to toss a coin." 4


A vice president at the American Cancer Society (ACS) said of animal drug tests, “They’re probably misleading. High doses of a particular compound given over a period of time may suggest carcinogenicity not so much from their innate carcinogenicity but the fact that they have caused so much tissue damage   that the risk of cancer increases.”


Researchers attempt to determine a substance’s carcinogenicity on animals, even when it is being used by humans without incident. Benzoyl peroxide, saccharin and a popular laxative were found to cause cancer in certain rats, though human use of these products for years without incident indicated their safety. The only benefit of these studies, and others like them, is the vivisectors’ financial gain.


Determining human carcinogens by testing on animals has yet to provide us with accurate results. Instead, it has delayed medical progress, costing us our health, lives, and tax dollars. Known human carcinogens have been determined through non-animal means, and can be read about further in the section “Replacing Animals in Cancer Research.”

1. Lancet, 827-8 (15 April 1972).

2. F.K. Ennever, et al., Mutagenesis 2 (1987): 73-8.

3. D. Salsburg, Fundamental and Applied Toxicology 3 (1983): 63-7.

4. L.B. Lave, et al. Nature 336 (1988) 632-3.