RADIATION INDUCED VERTEBRAL OSTEOSARCOMA FOLLOWING TREATMENT OF AN INTRADURAL EXTRAMEDULLARY SPINAL CORD TUMOR IN A DOG

A 2-year-old neutered female Rottweiler diagnosed with an intradural extramedullary spinal cord tumor at T12-T13 was successfully treated with cytoreductive surgery followed by Cobalt 60 teletherapy. The dog was euthanised 5-and-a-half years later following diagnosis of an osteosarcoma involving the L1 and L2 vertebrae. Evidence of the initial tumor was not present at necropsy. The vertebral neoplasm fulfilled all of the accepted criteria for a radiation induced tumor. It was concluded that adjunctive irradiation should be considered for treatment of intradural extramedullary tumors of young dogs when total surgical resection is not possible. Although tumor induction is a rare late effect of radiation therapy, the risk of this occurrence should be considered when irradiating young animals. Radiation induced tumors in dogs have been associated with coarse fractionation schemes, or when large intraoperative doses have been administered. A lower dose per fraction, e.g., 3 Gy/fraction or less, is advisable when irradiating young dogs or any dog in which the life expectancy is 3-5 or more years after irradiation.     

A SURVEY OF VETERINARY RADIATION FACILITIES IN THE UNITED STATES DURING 2001

A survey of veterinary radiation therapy facilities in the United States was done in 2001 to determine the type of equipment available, radiation protocols used, case load, tumor types irradiated, as well as other details of the practice of radiation oncology. A total of 42 sites were identified and included 17 (40%) academic institutions, and 25 (60%) private practice external beam radiation facilities. The overall response rate was 79% (33/42 responded). Based on this survey there is substantial variation between facilities in all aspects ranging from equipment and personnel to radiation protocols and caseloads. American College of Veterinary Radiology boarded radiation oncologists direct 76% of the radiation facilities at academic institutions and 60% of the private practice facilities. Three facilities had orthovoltage radiation units only, and 30 facilities had mega-voltage equipment: cobalt 60 or linear accelerator. A total of 18 facilities had linear accelerators with three of these off site at a human radiation facility. Patient load information was available from 31 sites (74% of the radiation facilities in the United States), and based on the responses 2790 dogs and 1081 cats were irradiated in 2001. Canine mast cell tumors were the most frequently irradiated tumor. This represents the first survey of veterinary radiation facilities in the United States and provides information on the specialty of veterinary radiation oncology.