Toxicity and efficacy of a novel doxorubicin and carboplatin chemotherapy protocol for the treatment of canine appendicular osteosarcoma following limb amputation

Objective To evaluate the safety and efficacy of a novel doxorubicin and carboplatin chemotherapy protocol for the treatment of dogs with appendicular osteosarcoma following limb amputation. Design Retrospective study. Procedure Dogs diagnosed with appendicular osteosarcoma, with no evidence of metastatic disease, treated with amputation and adjuvant chemotherapy consisting of two doses of doxorubicin given 14 days apart, followed by four doses of carboplatin at 3-weekly intervals between September 2003 and December 2009 were identified from the medical records of Perth Veterinary Oncology. Haematological and gastrointestinal toxicities were assessed based on information in the medical records and recorded complete blood count results. The efficacy of the protocol was assessed by determining the median disease-free interval ( DFI) and overall survival time ( OST) using the Kaplan-Meier product-limit method. Results In total, 33 dogs met the inclusion criteria. The median DFI was 231.5 days and the median OST was 247 days. With regard to haematological toxicity, 56% of dogs had a grade 1-2 neutropenia recorded as their highest marrow toxicity and 9% of dogs experienced a grade 3-4 neutropenia, all subsequent to doxorubicin administration. The highest gastrointestinal toxicity was grade 1-2 in 15 dogs ( 47%) and 5 dogs ( 16%) experienced grade 3-4 gastrointestinal toxicity. Conclusion This chemotherapy protocol did not result in a longer time to disease recurrence or OST in this population of dogs. Dualagent protocols have failed to improve survival times and therefore we conclude that a single-agent protocol using carboplatin may be equally effective with less toxicity.