Four fraction palliative radiotherapy for osteosarcoma in 24 dogs.

Twenty-four dogs underwent palliative radiotherapy consisting of four 8 gray (Gy) fractions of 60Co radiation on days 0, 7, 14, and 21 at 26 sites for axial (n=11) or appendicular (n=15) osteosarcoma. Response was noted in 92% of sites treated. Seventeen dogs were euthanized due to local or metastatic disease, one dog died of metastatic disease, five dogs died of unrelated causes, and one dog is alive. The four fraction protocol is effective for palliation of clinical signs associated with axial or appendicular osteosarcoma and may result in a higher response rate and longer survival time than three fraction palliative protocols.