Evaluation of the risk and age of onset of cancer and behavioral disorders in gonadectomized Vizslas

• Localización: JAVMA: Journal of the American Veterinary Medical Association, ISSN-e 0003-1488, Vol. 244, Nº. 3, 2014, págs. 309-319
• Idioma: inglés
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• Resumen

  • Objective�To investigate associations between age at gonadectomy and estimated risk or age at diagnosis of neoplastic and behavioral disorders in Vizslas.

    Design�Retrospective cohort study.

    Animals�2,505 Vizslas born between 1992 and 2008.

    Procedures�Data on demographics, gonadectomy status, and age at diagnosis of disease or disorder were obtained with an anonymous online survey and analyzed.

    Results�Dogs gonadectomized at = 6 months, between 7 and 12 months, or at > 12 months of age had significantly increased odds of developing mast cell cancer, lymphoma, all other cancers, all cancers combined, and fear of storms, compared with the odds for sexually intact dogs. Females gonadectomized at = 12 months of age and males and females gonadectomized at > 12 months of age had significantly increased odds of developing hemangiosarcoma, compared with the odds for sexually intact dogs. Dogs gonadectomized at = 6 months of age had significantly increased odds of developing a behavioral disorder. The younger the age at gonadectomy, the earlier the mean age at diagnosis of mast cell cancer, cancers other than mast cell, hemangiosarcoma, lymphoma, all cancers combined, a behavioral disorder, or fear of storms.

    Conclusions and Clinical Relevance�Additional studies are needed on the biological effects of removing gonadal hormones and on methods to render dogs infertile that do not involve gonadectomy. Veterinarians should discuss the benefits and possible adverse effects of gonadectomy with clients, giving consideration to the breed of dog, the owner's circumstances, and the anticipated use of the dog.

    Veterinarians, breeders, and owners have a particular interest in the health of purebred dogs. Estimating the risk of various diseases in a given breed can be helpful in guiding diagnostic decisions of veterinarians and can identify factors that might contribute to or accompany these disease conditions. Such knowledge can also guide breeders in selection and testing of breeding pairs, help national breed clubs direct their fundraising efforts to support research on the most common diseases that affect their specific breeds of dog, and inform the public regarding health issues that might be encountered when purchasing or adopting dogs of a specific breed.

    In 2008, the Vizsla Club of America Welfare Foundation sponsored and funded the Vizsla Health Survey to examine health issues in that breed.1 The survey identified cancer and behavioral problems as the most prevalent diseases or disorders in the breed. Of the 2,505 dogs reported, 604 (24.1 %) had at least 1 type of cancer and 648 (25.9%) had behavioral disorders.1 Cancer, specifically hemangiosarcoma and lymphoma, was listed as the most common cause of death in the Vizsla breed. Mast cell cancer, hemangiosarcoma, and lymphoma or lymphosarcoma were the leading types of cancer in the breed, and there was an association between gonadectomy and development of these cancers as well as between gonadectomy and behavioral problems.1 Investigators in a number of studies have found associations between gonadectomy and an increased risk of various types of cancer, including hemangiosarcoma,2,3 prostate cancer,4�8 transitional cell carcinoma,6,9�11 and osteosarcoma.12�14 Investigators in other studies15�20 have found an association between gonadectomy and behavioral problems. Given the results of these studies and the association between cancer and behavioral problems and gonadectomy in Vizslas,1 we were interested in determining whether there was a relationship between the risk of these problems and age at gonadectomy. Cancer was of particular interest because it is a major veterinary expense for owners and one of the most common causes of early death in dogs.21 Studies on the association between gonadectomy and orthopedic conditions, such as cranial cruciate ligament insufficiency,22�25 hip dysplasia,20,26 and patellar luxation,27 have been published. Orthopedic disorders are uncommon in Vizslas.1 The association between various orthopedic conditions and gonadectomy has been studied extensively in breeds more prone to such disorders; thus, we did not believe it necessary to evaluate the relationship between orthopedic conditions and gonadectomy in Vizslas.

    Whether the increased risks for cancer and behavioral problems differ between male and female Vizslas gonadectomized at various ages was also considered important. This information would allow veterinarians and breeders to make recommendations regarding the optimal age at which dogs should undergo gonadectomy. This is particularly important for female dogs because it is thought that there is an increasing risk for mammary gland cancer28,29 and pyometra30�32 in bitches that remain sexually intact for a longer period before gonadectomy.

    Therefore, the purpose of the study reported here was to examine data obtained in the study1 on Vizslas to determine whether age at gonadectomy or sex of gonadectomized dogs altered the risks of cancer or behavioral problems or age of onset of these conditions. We hypothesized that even though the study1 on Vizslas revealed differences in the estimated risk of cancer and behavioral problems between sexually intact dogs and dogs gonadectomized at any age, gonadectomy after puberty might not be associated with an increased risk. In other words, the associations detected in that study might have been a function of only prepubertal gonadectomy. In addition, we considered that analysis of age at diagnosis might provide additional information to support or refute findings in that study1 of an increased risk of cancer and behavioral problems in gonadectomized dogs.