Prognostic factors for radiation treatment of mast cell tumor in 85 dogs.

Ninety-five mast cell tumors in 85 dogs were therapeutically irradiated. Median and mean tumor-free times for dogs were 17 and 62.7 months, respectively. Percentages of dogs tumor-free at 1 and 2 years were 78.8 and 77%, respectively. Factors significantly affecting tumor-free time were clinical stage (P less than 0.001) and neoplasm location (P = 0.019). Median and mean survival times were 19 and 61.2 months, respectively. Survival rates at 1 and 2 years were 76.2 and 73.2%, respectively. Prognostic factors that significantly affected survival rates were clinical stage (P less than 0.001), neoplasm grade (P = 0.006), and neoplasm location (P = 0.034). Radiation therapy was an effective treatment of mast cell tumor in dogs.