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 extram edullary spinal cord tumor at T12-T13 was successfully treated with cytored uctive surgery followed by Cobalt 60 teletherapy. The dog was euthanised 5- and-a-half years later following diagnosis of an osteosarcoma involving the Ll and L2 vertebrae. Evidence of the initial tumor was not present at necr opsy. The vertebral neoplasm fulfilled all of the accepted criteria for a r adiation induced tumor. It was concluded that adjunctive irradiation should be considered for treatment of intradural extramedullary tumors of young d ogs when total surgical resection is not possible. Although tumor induction is a rare late effect of radiation therapy, the risk of this occurrence sh ould be considered when irradiating young animals. Radiation induced tumors in dogs have been associated with coarse fractionation schemes, or when la rge intraoperative doses have been administered. A lower dose per fraction, e.g., 3 Gy/fraction or less, is advisable when irradiating young dogs or a ny dog in which the life expectancy is 3-5 or more years after irradiation.