P. 535

A.T. Kristensen1, M.M.E. Larsen1
1University of Copenhagen, Department of Veterinary Clinical Sciences, Copenhagen, Denmark
Androgens, oestrogen and progesterone are all steroid hormones produced mainly in the gonads of both male and female dogs in varying amounts. Small amounts are produced in other tissues, such as the adrenals,
in amounts overall negligible in the intact individual. These extra gonadal production sites may increase their production in the gonadectomised individual.
Steroid hormones have hydrophobic properties, and diffuse passively across cell membranes. The hormonal receptors are nuclear transcription factors, bound to the nuclear DNA, and when activated by different processes, result in gene transcription. The tissue and cellular distribution of the different receptors determines the physiological effect of the hormone-hormone receptor binding.
Gonadal hormones are needed to obtain the sexual characteristics for the individual as whole and for development of speci c tissues in the dog, as well
as other mammals. Oestrogen and progesterone are hormones essential to the normal development of mammary tissue in the female, and early gonadectomy will hinder the natural proliferation of tissue and thereby decrease the risk of mammary neoplasia. Contrary to previous beliefs, gonadectomy in the mature female has been shown to exert a preventive effect on neoplastic development of the mammary glands (1,2). In the male dog, androgens promote perianal adenomas, but seems to have a protective effect against prostate tumours (3).
In 1999, Ware showed a signi cant correlation between gonadectomised females and cardiac haemangiosarcoma (4), and since then several studies have shown correlations between gonadectomy and several cancers outside the reproductive system, previously believed to be independent of gonadal hormones (5–10).
Signi cant correlations have been shown for mast cell tumour, lymphoma, haemangiosarcoma and osteosarcoma. Several studies are breed speci c and in a retrospective case-control study of Hart and others (9) a difference was found between incidence of cancer in gonadectomised Golden Retrievers and Labrador Retrievers, suggesting that there is a true breed difference to the in uence of gonadectomy on occurrence of speci c cancers.
The incidence of cancer is normally low within a population, with a long induction time, therefore prospective studies are not economically and time-wise considered feasible. When the incidence of disease is low, large populations are needed when analyzing for risk factors. Accordingly studies are mostly case-control studies, or retrospective cohort studies within a breed with a high breed prevalence, as for Cooley et al (7) in the study of correlation of osteosarcoma within a cohort of Rottweiler.
In human cancer medicine, public registration is mandatory in many countries resulting in large, multi- institutional data collection. In companion animals, national cancer registries exist in smaller numbers and many inactive. One of the larger, active databases is The Veterinary Medical Database (VMDB), initiated in 1964 and still receiving registrations.
In Denmark, the Danish Veterinary Cancer Registry
was established in 2005, based on the University of Copenhagen and supported by The Danish Kennel Club. The registry is web-based and voluntary, collecting data of registered neoplasm of dogs and cats across the country.
In 2014, a preliminary study showed signi cant correlation between gonadectomy and several cancers outside the reproductive system, while no correlation was shown for other investigated cancers. The results were presented as an abstract at ECVIM 2014, and further studies are ongoing.
In Denmark dogs are not routinely gonadectomised before puberty contrary to many other countries, which gives a unique possibility to investigate the correlation between timing of gonadectomy and cancer incidence. Therefore a study was carried out, correlating the age at gonadectomy to occurrence of any of the four cancers; mast cell tumour, lymphoma, hemangiosarcoma and osteosarcoma, showing signi cant correlation for age of gonadectomy and occurrence of some cancers. These  ndings are supported by previous studies, though the results are not directly comparable as the strati cation of age at gonadectomy were different between studies (5,7,8). Selected data from the preliminary study and the current study will be presented at the WSAVA 2017 conference.
1. Sorenmo KU, Shofer FS, Goldschmidt MH. Effect of Spaying and Timing of Spaying on Survival of Dogs with Mammary Carcinoma. J Vet Intern Med [Internet]. 2000;14(3):266–70. Available from: http://doi.wiley. com/10.1111/j.1939-1676.2000.tb01165.x
2. Kristiansen VM, N??dtvedt A, Breen AM, Langeland M, Teige J, Goldschmidt M, et al. Effect of Ovariohysterectomy at the Time of Tumor Removal in Dogs with Benign Mammary Tumors and Hyperplastic Lesions: A Randomized Controlled Clinical Trial. J Vet Intern Med. 2013;27(4):935–42.
An Urban Experience

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