Studies have suggested that bisphosphonates provide significant benefits to humans with a wide variety of cancers. They may be particularly useful for local tumor control in large-breed veterinary patients with osteosarcoma for whom amputation and chemotherapy may be challenging. This case report describes using the bisphosphonate zoledronic acid in a 10-year-old Corso dog with right-foreleg lameness. A full clinical workup and biopsies resulted in a diagnosis of high-grade osteosarcoma without chest metastases. Treatment options included chemotherapy and amputation, palliative radiation therapy, cyclooxygenase-2 inhibitor immunotherapy, or palliative therapy with osteolytic activity inhibitors. The dog owners elected palliative antiresorptive therapy with zoledronic acid alone, and the patient received regular therapy every 28 days. Although the primary bone lesion enlarged over time, the patient showed stable, nonmetastatic disease for 16 months. A prescapular mass was identified after 16 months of therapy, and biopsy revealed lymph node metastasis of the primary bone tumor. All therapy was discontinued at this time. This study identified zoledronic acid as a palliative therapeutic option for osteosarcoma that resulted in probable local tumor control, high tolerability, decreased pain, and improved quality of life.

COMMENTARY: This article describes a remarkable response to the injection of the bisphosphonate zoledronic acid, one of several methods of palliative pain management in dogs with primary bone tumors. Although the bioavailability in dogs is highest with injectable formulations, the effect is expected to last 4 to 6 months. Another option is to combine injectable bisphosphonates with palliative radiation therapy as a way to improve rate and duration of response.

Zoledronic acid for the treatment of appendicular osteosarcoma in a dog. Spugnini EP, Vincenzi B, Caruso G, et al. J SMALL ANIM PRACT 50:44-46, 2009.