Early outcomes of Image-Guided Hypofractionated Volumetric Modulated Arc Radiotherapy (IG-HyVMAT) in dogs with Non-Lymphomatous Nasal Tumors (NLNT)

Abstract

Radiotherapy is a cornerstone in the management of canine non-lymphomatous nasal tumors (NLNT), providing both palliative benefit and local tumor control. Image-Guided Hypofractionated Volumetric Modulated Arc Radiotherapy (IG-HyVMAT) has recently emerged as a promising treatment modality for canine sinonasal tumors; however, data regarding tumor control, radiation-associated morbidity, and treatment outcomes across specific tumor histotypes remain limited. This retrospective study evaluated treatment response as well as early and late toxicities in 12 dogs with NLNT treated using IG-HyVMAT or IG-HyVMAT with a simultaneous integrated boost (SIB) protocol. Tumors were staged using a modified veterinary radiotherapy staging system, and treatment-related toxicities were assessed according to the Veterinary Radiation Therapy Oncology Group (VRTOG) criteria. IG-HyVMAT, most commonly delivered in combination with SIB, was prescribed at doses ranging from 25 to 40 Gy. The treatment protocols were well tolerated and associated with minimal acute toxicity. Clinical signs such as dyspnea and nasal congestion were identified as important prognostic indicators for survival in dogs with NLNT. The observed overall survival time (OST) and progression-free survival time (PFST), together with the low incidence of acute adverse effects, suggest that the SIB approach may offer potential clinical benefits, particularly in cases requiring palliative treatment. Overall, the findings of this study indicate that IG-HyVMAT, frequently applied with SIB, may provide meaningful survival advantages in dogs with NLNT while maintaining an acceptable toxicity profile. Nevertheless, further studies incorporating more advanced dose-optimization strategies for adjacent critical organs are warranted.