Superficial kilovoltage x-ray radiotherapy for the treatment of cutaneous mast cell tumors on the head in three dogs and one cat: a limited retrospective case series.

Abstract

To report preliminary findings of hypofractionated superficial radiotherapy for treatment of cutaneous mast cell tumors (MCTs) and report the acute and late toxicity associated with its use. 3 dogs and 1 cat. In this retrospective study, medical records from January 2021 through July 2022 were searched for animals that received superficial radiation therapy for MCTs of the head. 4 patients with 5 MCTs were included. Three of the masses were periocular and required protection of the globe with a tungsten eye shield. One patient did not complete the intended protocol due to diffuse metastatic spread noted after the second fraction. Of the 3 patients that completed their protocol, 100% had a complete response. Two canine patients were treated adjunctively with toceranib. Two of the 4 patients experienced grade 1 acute veterinary radiation therapy oncology group (VRTOG) toxicity, and the 3 patients that completed their protocol experienced grade 1 late VRTOG toxicity. No radiation effects were documented to the cornea or lens in any patient. Superficial radiation therapy was effective in our limited study population, and patients experienced minimal side effects for treatment of cutaneous MCTs.