Radiation treatment for incompletely resected soft-tissue sarcomas in dogs

Objective-To evaluate efficacy of radiation for treatment of incompletely r esected soft-tissue sarcomas in dogs. Design-Prospective serial study. Animals-48 dogs with soft-tissue sarcomas. Procedure-Tumors were resected to < 3 cm(3) prior to radiation. Tumors were treated on alternate days (three 3-Gy fractions/wk) until 21 fractions had been administered. Cobalt 60 radiation was used for all treatments. Results-Five-year survival rate was 76%, and survival rate was not differen t among tumor types or locations. Four (8%) dogs developed metastases. Eigh t (17%) dogs had tumor recurrence after radiation. Development of metastase s and local recurrence were significantly associated with reduced survival rate. Median survival time in dogs that developed metastases was 250 days. Median disease-free interval for all dogs was 1,082 days. Median time to re currence was 700 days. Dogs that developed recurrence after a prolonged per iod responded well to a second surgery. Acute radiation toxicosis was minim al; osteosarcoma developed at the radiation site in 1 dog. Conclusions and Clinical Relevance-An excellent long-term survival rate may be achieved by treating soft-tissue sarcomas in dogs with resection follow ed by radiation. Amputation is not necessary for longterm control of soft-t issue sarcomas in limbs. Development of metastases and recurrence of local tumors after radiation treatment are associated with decreased survival rat e. Acute and delayed radiation toxicosis was minimal with the protocol used in this study.