Orthovoltage radiotherapy of oral fibrosarcomas in dogs.

Seventeen dogs with oral fibrosarcomas were referred for radiotherapy. All dogs were treated with orthovoltage x-rays at doses that approached the tolerance level of normal tissue. Acceptable normal tissue complications (epilation, mucositis, and moist desquamation) developed in all dogs surviving radiotherapy. Osteonecrosis, an unacceptable complication of radiotherapy, developed in 2 dogs. Of the 17 treated dogs, 2 died before radiotherapy was completed and 2 lived less than 1 month after treatment. One of the 17 was alive, with osteonecrosis, 27 months after radiotherapy and was free of tumor. The mean time to tumor regrowth and mean survival time in the other 12 dogs were 3.9 and 6.8 months, respectively. The results indicated a poor response of oral fibrosarcomas to treatment with orthovoltage x-rays. It was concluded that treatment of oral fibrosarcomas with other modalities, eg, 60Co gamma rays, may lead to improved results.