Some prognostic and epidemiologic factors in canine osteosarcoma.

Naturally occurring skeletal osteosarcomas in a series of 144 untreated dogs were found especially to involve the ends of the long bones of the forelimbs and affected predominantly older male dogs of giant and large breeds. Most tumors were large and partially necrotic and had extended into soft tissues. Of 12 host and tumor characteristics tested in the first part of the study, tumor diameter and volume were significantly associated with the presence of pulmonary metastases at autopsy. The second part of the study revealed that extension of the tumor into the soft tissues and localization of the tumor in the hind legs were associated with a poor prognosis, whereas the fibrosarcomatous type of tumor was associated, as in man, with a favorable prognosis. An association between the 12 characteristics tested was found in 11 of 78 combinations at the 5% level and in 5 combinations at the 1% level. Affected giant dogs were generally younger than affected small and medium-sized dogs. Especially in giant dogs, the osteosarcomas involved the long bones and were of relatively large diameters. The sarcomas in female dogs were larger in volume than those in males. Pure osteoblastic osteosarcomas were generally smaller than combined (chondroblastic and fibroblastic) osteosarcomas. Peritumorous lymphocytes and plasma cells were present in 50% of the dogs, especially in small and young dogs. When compared with a reference population, great Danes, rottweilers, German shepherds, and boxers were found to be overrepresented in the osteosarcoma group.