Outcome and prognostic factors for osteosarcoma of the maxilla, mandible, or calvarium in dogs: 183 cases (1986-2012)

Objective—To describe the biological behavior, clinical outcome, and prognostic factors of osteosarcoma of the maxilla, mandible, or calvarium in dogs.

Design—Retrospective case series.

Animals—183 client-owned dogs with osteosarcoma of the maxilla, mandible, or calvarium.

Procedures—Medical records for dogs treated for osteosarcoma of the maxilla, mandible, or calvarium from 1986 through 2012 were reviewed. Dogs with a histopathologic diagnosis of osteosarcoma and treated for a primary tumor arising from these bones of the head were included.

Results—Mean age was 9.3 years, and body weight was 31.8 kg (70.0 lb). Most dogs (124/183 [67.8%]) were purebred, and the most common primary tumor site was the maxilla (80 [43.7%]). Treatments included palliative medical treatment only (11/183 [6.0%]), coarsely fractionated radiation therapy (RT; 12 [6.6%]), fractionated or stereotactic RT (18 [9.8%]), surgery (135 [73.8%]), and both surgery and fractionated RT (7 [3.8%]). Eightythree (45.4%) dogs received adjuvant chemotherapy. Local recurrence or progression occurred in 80 of 156 (51.3%) dogs, and 60 of 156 (38.5%) dogs developed distant metastases. Median survival time for all dogs was 239 days. Dogs that underwent surgery had a median survival time of 329 days. Histologically tumor-free surgical margins were associated with significantly decreased hazards of progression or recurrence (hazard ratio [HR], 0.4) and death (HR, 0.5). Dogs with osteosarcoma of the calvarium had a significantly greater hazard of local recurrence or progression (HR, 2.0).

Conclusions and Clinical Relevance—In this study, tumor excision in dogs with histologically tumor-free margins resulted in better local control and longer survival time than did other treatment types.