Research Update: The prevalence of and risk factors for canine appendicular osteosarcoma

In this retrospective study of dogs treated at a veterinary teaching hospital, the prevalence of appendicular osteosarcoma in greyhounds compared with other breeds was examined, along with the potential risk factors for developing the disease. Primary appendicular osteosarcoma was diagnosed in 179 dogs; prevalence was highest for greyhounds (6.2%), rottweilers (5.3%), and Great Danes (4.4%). All of the greyhounds were retired from racing or training. Body weight and sex were not risk factors for osteosarcoma in these breeds; however, risk did increase with age. Greyhounds were significantly older at the time of diagnosis (mean = 9.9 years) than were rottweilers (mean = 8.3 years) and Great Danes (mean = 7.8 years). Rottweilers and Great Danes were more likely to have osteosarcoma in the forelimbs than in the hindlimbs. The most frequent sites for osteosarcoma in all three breeds were the proximal end of the humerus and distal region of the radius. In greyhounds, the proximal aspect of the femur was also a common site for osteosarcoma.

The authors recognized the limitations of a retrospective study involving low osteosarcoma case numbers and potential geographic bias (a state with the largest number of greyhound racetracks and retired animals in the country). Nonetheless, the three breeds listed were shown to have an increased risk for osteosarcoma compared with mixed-breed dogs.

COMMENTARY

Bone neoplasia is a morbid and common condition encountered in small-animal practice. Osteosarcoma is the most common primary bone tumor in dogs; large and giant breeds, such as Irish wolfhounds, Scottish deerhounds, and Borzois, have an increased risk for developing osteosarcoma. The lesions most frequently involve the proximal end of the humerus and distal end of the radius. The results of this study reveal that another sight hound, the greyhound, may also be at risk for developing osteosarcoma and that the proximal aspect of the femur may be another frequent location for the lesion. In the three most commonly affected breeds of this study, age was a risk factor while body weight and sex were not. To their credit, the authors cited numerous previous studies both in agreement and in conflict with this data. Furthermore, the speculation of trauma-induced neoplasia in racing greyhounds could not be ascertained because of the absence of a control (nonracing, nontraining greyhounds). Theoretically, the greater weight carried by the forelimbs (60%) and the increased stress on the right limbs in dogs racing counterclockwise could be factors in the development of osteosarcoma. Interestingly, the greyhounds in this report did not have an increased risk in the forelimbs or in the right vs. left limbs.

Rosenberger JA, Pablo NV, Crawford PC. Prevalence of and intrinsic risk factors for appendicular osteosarcoma in dogs: 179 cases (1996-2005). J Am Vet Med Assoc 2007;231(7):1076-1080.

The information in "Research Updates" was provided by Veterinary Medicine Editorial Advisory Board member Joseph Harari, MS, DVM, DACVS, Veterinary Surgical Specialists, 21 E. Mission Ave., Spokane, WA 99202.

Joseph Harari