Response of canine mast cell tumors to radiation

Twenty-three dogs completed a fractionated course of ionizing radiation therapy for mast cell tumors. In 10 dogs the response was satisfactory, and the tumors were considered controlled 12 months after completion of the prescribed course of therapy. Treatment was considered unsatisfactory for the remaining 13 dogs due to failure to control the tumor locally, generalized metastasis, or both. A dose effect was noted in the response of the tumors to radiation. Of 6 dogs, 5 responded satisfactorily when the tumor dose was 4,000 rads or greater. When the tumor dose was less than 4,000 rads, 5 of 17 dogs responded satisfactorily. The dose calculated to control 50% of the meat cell tumors was 3,625 rads (95% confidence interval: 3,265-4,024 rads). Adverse normal tissue reactions, which consisted of moist desquamation in 10 animals and necrosis in 4, were recorded. The dose calculated to cause desquamation in 50% of the dogs was 3,750 rads (95% confidence interval: 3,348-4,200 rads).