Radiation Therapy for Osteosarcoma

Osteosarcoma (OSA) is the most common primary bone tumor in dogs. Limb amputation remains standard treatment for local control; however, radiation therapy has become more common as availability has increased and targeting improved. A major challenge of any limb salvage technique is pathologic bone fracture.

This small retrospective study described the clinical features of 6 dogs with appendicular OSA managed by stereotactic radiosurgery (SRS; radiation therapy that focuses high-power energy on a small area of the body), adjuvant chemotherapy, and fracture fixation for secondary pathologic fractures. The mean time to fracture development after SRS was 6.25 months for the 4 cases that did not initially present with pathologic fractures. Five cases developed early postoperative surgical infections after fracture stabilization and required extended antimicrobial therapy and/or wound debridement. Implant failure occurred in 50% of cases; 2 revisions and 1 amputation were required. When morbidity was controlled, subjective limb function was good in all cases, despite intermittent lameness. The overall survival ranged from 364–897 days, with metastatic disease developing in 4 of 6 cases; 1 dog was lost to follow-up.

Limb-sparing alternatives for appendicular bone tumors have seen an increase in usefulness, particularly with advanced focused radiation therapy and surgical techniques to preserve limb function and comfort. Pathologic fracture remains a major challenge for all techniques, especially radiation, which weakens the already damaged cortical bone, leading to radiation-induced bone necrosis and resulting in secondary fracture in >50% of cases. Fracture fixation can be considered for select cases, and bone plating is being used prophylactically in some institutions to lower this risk. However, infection and implant failure are highly prevalent and associated with substantial morbidity. Surgical strategies (eg, augmentation of bone with regenerative cells to promote healing, minimally invasive plating, other novel treatments) are needed to improve patient outcomes from this disabling disease.—Jason Bleedorn, DVM, DACVS

Stereotactic radiosurgery and fracture fixation in 6 dogs with appendicular osteosarcoma. Covey JL, Farese JP, Bacon NJ, et al. VET SURG 43:174-181, 2014.