Reproductive Status and Neoplasia Incidence in Golden Retrievers

Several recent studies have investigated possible correlations between reproductive status and neoplasia incidence in purebred dogs. The golden retriever is an overrepresented breed for several types of neoplasia, including hemangiosarcoma and lymphoma. In a study recently published in PLoS ONE, investigators examined the association between reproductive status and cancer in this specific breed.

Study Design

The investigators retrospectively examined veterinary records for golden retriever dogs undergoing necropsy examination at the University of California, Davis Veterinary Medical Teaching Hospital (VMTH). Signalment and pathologic diagnosis were recorded to determine cause of death and, when applicable, neoplasia type was categorized.

Statistical analyses were performed to explore relationships among age, sex, reproductive status, cause of death, and type of neoplasia.

Results

The records of a total of 8,756 golden retrievers from 1989 through 2016 were examined. Of these, necropsy was performed on 118 (18.1%) intact males, 228 (35.0%) neutered males, 58 (8.9%) intact females, and 248 (38.0%) spayed females. Natural death or euthanasia was attributed to neoplasia-related causes in 65% (424/652) of all necropsied dogs.

The distribution of cancers in golden retrievers that died of neoplasia-related causes were as follows:

• 96 dogs (22.6%) with hemangiosarcoma
• 78 dogs (18.4%) with lymphoid neoplasia
• 55 dogs (13.0%) with carcinomas
• 37 dogs (8.7%) with meningioma
• 33 dogs (7.8%) with histiocytic neoplasia
• 29 dogs (6.8%) with osteosarcoma
• 9 dogs (2.1%) with melanoma
• 7 dogs (1.7%) with pituitary tumor
• 42 dogs (9.9%) with other sarcomas
• 38 dogs (9.0%) with “other cancers”

The median age at death of dogs with cancer was significantly higher than that of dogs dying of non—cancer-related causes (9.8 vs. 6.9 years), which held true for all 4 categories of dogs based on reproductive status (intact males, neutered males, intact females, and spayed females). Odds ratio analysis showed that the highest likelihood of cancer-related mortality occurred below 11.6 years of age.

The median age of spayed female dogs at death was significantly higher than that of intact females (9.5 vs. 5.9 years), while intact and neutered males had similar median ages at death (8.7 and 9.4 years, respectively). The investigators attributed the overall low median age at death to the referral nature of the hospital, suggesting that median lifespan is longer in the general population of golden retrievers.

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A greater proportion of spayed females died of cancer compared with intact females, while neuter status did not affect the proportion of male dogs that died of cancer. Incidences of each neoplasia type were statistically similar in intact and gonadectomized dogs. Further description of non-neoplasia—related causes of death was beyond the scope of the study and thus not evaluated.

Conclusions

The study showed that neoplasia-related deaths in golden retrievers occur relatively later in life compared with non—neoplasia-related deaths. In particular, intact female dogs died at a younger age, but had a lower incidence of neoplasia, than did spayed females. However, gonadectomy status did not correlate with any particular type of neoplasia.

Dr. Stilwell received her DVM from Auburn University, followed by a MS in Fisheries and Aquatic Sciences and a PhD in Veterinary Medical Sciences from the University of Florida. She provides freelance medical writing and aquatic veterinary consulting services through her business, Seastar Communications and Consulting.