Samarium Sm 153 lexidronam for the palliative treatment of dogs with primary bone tumors: 35 cases (1999-2005)

Objective - To evaluate survival times and palliative effects associated with the use of samarium Sm 153 lexidronam in dogs with primary bone tumors. Design-Retrospective case series. Animals - 35 dogs with primary appendicular (n = 32) or axial (3) bone tumors. Procedures - 1 to 4 doses of samarium Sm 153 lexidronam were administered at a rate of 37 MBq/kg (16.8 MBq/lb), IV. Response to treatment, measured by lameness improvement, and survival time were determined. Results - Of the 32 dogs with appendicular tumors, 20 (63%) had an improvement in the severity of lameness 2 weeks after administration of the first dose of radioactive samarium, 8 (25%) had no change in the severity of lameness, and 4 (12%) had a worsening. Overall median survival time was 100 days, with 3 dogs (8.6%) alive after 1 year. Median survival time for the 32 dogs with appendicular tumors was 93 days, with 3 (9.4%) alive after 1 year. This was not significantly different from the median survival time of 134 days for a historical cohort of 162 dogs with appendicular osteosarcoma that underwent amputation as the only treatment. Conclusions and Clinical Relevance - Results suggest that samarium Sm 153 lexidronam may be useful in the palliation of pain in dogs with primary bone tumors that are not candidates for curative-intent treatment.