Hypofractionated radiation therapy for invasive thyroid carcinoma in dogs:a retrospective analysis of survival

Thirteen dogs with invasive thyroid carcinoma (WHO classification T2b or T3 b) seen between January 1991 and October 1997 were treated by external beam Irradiation. Four once-weekly fractions of 9 gray of 4 MeV X-rays were adm inistered. Four of the dogs died of progression of the primary disease and four from metastatic spread. Of the remaining dogs, three died of unrelated problems, although two were still alive at the time of the censor. Kaplan- Meier analysis of the survival time from first dose to death from either pr imary or metastatic disease gave a median survival time of 96 weeks (mean 8 5 weeks, range six to 247 weeks). Radiographic evidence of pulmonary metast atic disease at presentation had no prognostic value whereas crude growth r ate was a highly significant factor. The present series Indicates that radi ation therapy should be considered an important modality for the control of invasive thyroid carcinoma in the dog.