- Toft, J. D. 1992. Commonly observed spontaneous neoplasms in rabbits, rats, guinea pigs, hamsters, and gerbils. Semin. Avian Exotic Pet Med 1:80.
- The Biology of the Laboratory Rabbit, 1994 edition.
TBLR provides the following information: Adenocarcinoma of the uterus is the most frequently encountered neoplasm of the rabbit. Ingalls (J. Natl. Cancer Inst. 33:799-806. 1964) showed that 11 of 12 rabbits developed uterine carcinoma. Because of the number of rabbits developing carcinoma many researchers looked into the possibility of estrogen being carcinogenic. There was quite a bit of conflicting data, and the authors draw this conclusion “Data is extremely difficult to interpret because of the naturally high incidence of adenocarcinoma of the uterus in untreated rabbits.”Later, “Notwithstanding heredity as a factor, the incidence of uterine carcinoma has been noted to exceed 50% in certain colonies of random bred females kept past 5-6 years.”
- Ann NY Acad. Sci. 75:535-542 Green, 1958.
This is perhaps the best article, and probably where everyone gets the often quoted 80% figure. Greene monitored a colony of rabbits over a long period of time (8-10 years). All rabbits dying from whatever causes were necropsied. 16.7% of 849 rabbits were found to have uterine adenocarcinoma. The average age of the colony was greater than 4 years, which is important, because most lab rabbits are under 24 months of age. The tumor incidence in Greene’s colony was very closely linked to age. In rabbits dying between 2 and 3 years of age the incidence of cancer was 4.2%. In rabbits 5-6 years of age the incidence is 79.1% (the mythical 80%). Note: these rabbits did not necessarily DIE from the cancer, but there were tumors after their death.We don’t know what the different causes of death were, but they are listed as “natural”. The incidence of cancer in males and females is about the same in rabbits under two years of age, after that, the incidence in females dramatically increases over the males, primarily due to uterine cancer.
We found the article in TBLR because it was referenced in a journal that claimed that the incidence of cancer was somewhere between 1 and 4% in rabbits. That low figure was compiled from laboratory rabbits, most under 2 years of age. So, that figure agrees very well with Greene’s findings. When one starts looking at older rabbits the data drastically changes. Most of the veterinarians we’ve talked with seem to believe that this is very genetically controlled. TBLR even lists breeds that are not susceptible to uterine cancer. While 80% may not be a figure for all rabbits, it was for that colony. Other colonies have had >50% incidence of cancer.
Many thanks to Laura Tessmerfor researching the topic of uterine cancer.
