MEDICAL MANAGEMENT

Many owners of affected dogs do not perceive the outcome of surgery (with or without chemotherapy) to be worthwhile. In these instances, medical management of the primary tumor may be elected. Medical management typically consists of daily treatment with a nonsteroidal anti-inflammatory drug (NSAID) to alleviate the associated bone pain. When lameness worsens and is refractory to treatment with NSAIDs, oral formulations of various opioids may provide more effective pain control.

In human medicine, osteolytic bone diseases (e.g. bone metastases and hypercalcemia of malignancy) are often treated with a class of drugs called bisphosphonates.⁶⁴ Bisphosphonates reduce bone resorption by inhibiting osteoclast function.⁶⁴ There is only one clinical report of the use of bisphosphonates in dogs with spontaneously occurring osteosarcomas.⁶⁵ In this report, alendronate was used as palliative treatment in two cases of primary canine osteosarcoma, one affecting the tibia and the other affecting the maxilla. According to the report, both dogs remained comfortable, surviving for 12 and 10 months, respectively. However, since only two dogs were studied, there was no control group, and survival was the only parameter measured, it is difficult to conclude what benefit alendronate provided. This case report, along with evidence for efficacy in the treatment of various malignant bone diseases in people, has prompted veterinary clinicians to treat some cases of primary canine osteosarcoma with bisphosphonates. Recently, the bisphosphonates alendronate, pamidronate, and zoledronate have been shown to inhibit canine osteosarcoma cell growth in vitro, raising the possibility that bisphosphonates may also be helpful as adjunctive chemotherapeutic agents.^66-68

Amputation in conjunction with chemotherapy continues to be the most common and effective treatment available for dogs with appendicular osteosarcoma^5,41; however, new approaches are being developed that should prolong survival times and decrease morbidity. As the efficacy of treatments such as limb-salvage surgeries, radiation, and chemotherapy are established, practitioner and owner interest will grow.

Editors' Note: One of the authors, Dr. Charles A. Kuntz, developed the endoprosthesis method discussed above and receives compensation for every unit sold from Veterinary Orthopedic Implants, which manufactures the endoprostheses.

Carl T. Jehn, DVM
James P. Farese, DVM, DACVS
Daniel D. Lewis, DVM, DACVS
Department of Small Animal Clinical Sciences and the Center for Veterinary Sports Medicine
College of Veterinary Medicine
University of Florida
Gainesville, FL 32610-0126.

Nicole Ehrhart, VMD, MS, DACVS
The Animal Cancer Center
College of Veterinary Medicine
Colorado State University
Fort Collins, CO 80523.

Charles A. Kuntz, DVM, MS, DACVS
Regional Veterinary Referral Center
6651-F Backlick Road
Springfield, VA 22150

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