Diagnosis and clinical outcome of cats with primary appendicular bone tumors: 76 cases.

OBJECTIVE

To describe outcomes in cats with primary appendicular bone tumors treated with complete or partial amputation, with or without adjuvant chemotherapy.

METHODS

This retrospective study analyzed cats with histologically confirmed primary appendicular bone tumors treated surgically between 2008 and 2019. Data included signalment, clinical signs, tumor location, preoperative imaging, amputation level, adjunctive therapy, histologic characteristics, and oncologic outcomes.

RESULTS

76 cats were included, with osteosarcoma being the most commonly diagnosed tumor. Median survival time (MST) for cats with osteosarcoma was 469 days, with 1- and 2-year survival rates of 56.8% and 40.4%, respectively. The MST for cats with chondrosarcoma was 1,302 days, with 1- and 2-year survival rates of 91.7% and 66.7%. Overall metastatic rate was 32.9%, and 36.2% for osteosarcoma specifically; scapular tumors had the highest metastatic rate (87.5%). Preoperative pulmonary metastasis significantly shortened MST in cats with osteosarcoma (152 vs 573 days). In cats with osteosarcoma without preoperative pulmonary metastasis, adjuvant chemotherapy significantly improved MST (1,466 vs 440 days). Negative prognostic indicators for cats with osteosarcoma were increased age and presence of suspected metastasis at any time.

CONCLUSIONS

Appendicular osteosarcoma in cats had a good prognosis following amputation alone, despite a higher metastatic rate than previously reported; however, adjuvant chemotherapy significantly improved survival time in cats with nonmetastatic osteosarcoma. Appendicular chondrosarcoma had an excellent prognosis following definitive surgery alone.

CLINICAL RELEVANCE: Cats with nonmetastatic osteosarcoma at diagnosis should be treated with both definitive surgery and adjuvant chemotherapy.