Findings from the Swiss Feline Cancer Registry, 1965-2008

A comprehensive analysis of cancer in cats has recently been published in the Journal of Comparative Pathology.

The authors of the study used data from the Swiss Feline Cancer Registry to analyze the associations of sex, neutering, breed, age, and time with tumor type and location. The cancer registry includes records of 51,322 cats with 18,375 diagnosed tumors, spanning the years between 1965 and 2008.

A notable finding was the changing frequencies of fibrosarcoma and lymphoma over the 4 decades of registry data. Fibrosarcoma frequency increased from 0% of the tumor types identified in 1965 to about 20% during the 1990s, remaining at that level ever since. The authors suggest that this increase could be due to injection-site sarcomas linked to the feline leukemia vaccine, which became available in Switzerland in 1986.

The frequency of lymphoma, on the other hand, decreased over the years. Lymphomas comprised around 30% of tumor diagnoses from the early 1970s until the middle 1990s, when the frequency declined to between 10% and 15%. Because feline leukemia virus causes lymphoma, the authors theorize that this change is also related to use of the feline leukemia vaccine.

The most common feline tumor types reported were adenoma/adenocarcinoma, fibrosarcoma, lymphoma, and squamous cell carcinoma. Other findings included the following:

Age associations

Tumor frequency increased with age for all types and locations of tumors. Lymphoma was the most common tumor type in cats younger than 5 years.

Sex and neutering associations

The odds of tumor development were higher in neutered cats than in intact cats for many tumor types, although the differences were often small. Tumor odds were higher in intact cats only for females with mammary gland tumors. According to the authors, “[t]he benefit of neutering appears to be dependent on the age at which the procedure is performed.” Female cats had higher odds of developing adenoma/adenocarcinoma, malignant skin tumors, and tumors of the mammary gland and cardiorespiratory system. Male cats had higher odds of developing tumors in the oral cavity and pharynx.

Breed associations

• Fibrosarcoma and squamous cell carcinoma: Some breeds had significantly lower odds of developing these tumors than did European shorthair cats (the breed used as the standard to which others were compared). The authors note that this is the first study showing an association of breed with fibrosarcoma development.
• Lymphoma: The odds of lymphoma were higher in Oriental shorthairs and Somalis than in European shorthairs.
• Mammary gland tumors: Breeds with the highest odds of developing mammary tumors, compared with European shorthairs, were Oriental shorthairs, Somalis, Abyssinians, and Siamese.
• Gastrointestinal tumors: The odds of developing tumors of the gastrointestinal tract were higher in Siamese, Chartreux, and Somali cats than in European shorthairs.

Cancer registries are important data sources for epidemiological research, say the study authors, adding that cancer studies in animals can also facilitate research in humans. “Companion animals with spontaneously developing tumours are…valuable resources for investigating the complexity of human cancer pathogenesis, progression and therapy,” they write. “Pets and people share the same environment and are therefore exposed to similar risk factors.” Detailed analyses of animal tumors can help identify genes and environmental risk factors linked to cancer and may lead to new diagnostic techniques and treatment options.

Dr. Laurie Anne Walden received her doctorate in veterinary medicine from North Carolina State University in 1994. After an internship at Auburn University College of Veterinary Medicine, she returned to North Carolina, where she has been in companion animal general practice for over 20 years. Dr. Walden is also a board-certified Editor in the Life Sciences and owner of Walden Medical Writing.