Comparison of Carboplatin and Doxorubicin‐Based Chemotherapy Protocols in 470 Dogs after Amputation for Treatment of Appendicular Osteosarcoma

BACKGROUND: Many chemotherapy protocols have been reported for treatment of canine appendicular osteosarcoma (OSA), but outcome comparisons in a single population are lacking. OBJECTIVE: To evaluate the effects of protocol and dose intensity (DI) on treatment outcomes for carboplatin and doxorubicin‐based chemotherapy protocols. ANIMALS: Four hundred and seventy dogs with appendicular OSA. METHODS: A retrospective cohort study was performed comprising consecutive dogs treated (1997–2012) with amputation followed by 1 of 5 chemotherapy protocols: carboplatin 300 mg/m(2) IV q21d for 4 or 6 cycles (CARBO6), doxorubicin 30 mg/m(2) IV q14d or q21d for 5 cycles, and alternating carboplatin 300 mg/m(2) IV and doxorubicin 30 mg/m(2) IV q21d for 3 cycles. Adverse events (AE) and DI were evaluated. Kaplan–Meier survival curves and Cox proportional hazards regression were used to compare disease‐free interval (DFI) and survival time (ST) among protocols. RESULTS: The overall median DFI and ST were 291 days and 284 days, respectively. A lower proportion of dogs prescribed CARBO6 experienced AEs compared to other protocols (48.4% versus 60.8–75.8%; P = .001). DI was not associated with development of metastases or death. After adjustment for baseline characteristics and prognostic factors, none of the protocols provided a significant reduction in risk of development of metastases or death. CONCLUSIONS AND CLINICAL IMPORTANCE: Although choice of protocol did not result in significant differences in DFI or ST, the CARBO6 protocol resulted in a lower proportion of dogs experiencing AEs, which could be advantageous in maintaining high quality of life during treatment. DI was not a prognostic indicator in this study.