Development of non-pulmonary soft-tissue metastasis is not a poor prognostic indicator in dogs with metastatic appendicular osteosarcoma.

Objectives: To evaluate whether patient factors affect development of non-pulmonary soft-tissue metastases following treatment of canine appendicular osteosarcoma and to report and compare outcomes to those in dogs with pulmonary or osseous metastases.

Animals and procedure: The records of 3 veterinary teaching hospitals were reviewed to identify dogs that received definitive treatment for a primary appendicular osteosarcoma lesion and chemotherapy between January 2010 and June 2022. Dogs with non-pulmonary metastases following initial treatment were included. Descriptive statistics were calculated to summarize signalment information, and metastasis and survival times were compared between groups using Kaplan-Meier survival analysis and log-rank tests.

Results: Thirty-six and 109 dogs developed non-pulmonary soft-tissue metastases and pulmonary or osseous metastases, respectively, following initial treatment. No patient factors were significantly associated with development of non-pulmonary soft-tissue metastases. The median times to non-pulmonary soft-tissue metastasis or initial pulmonary or osseous metastasis were 220 and 169 d, respectively (P = 0.18); whereas overall median survival times were 250 and 270 d, respectively (P = 0.36).

Conclusion: Dogs with non-pulmonary soft-tissue metastases had similar disease-free intervals and survival rates to dogs with typical pulmonary or osseous metastases.