Response of Spontaneous Oral Tumors in Canine Cancer Patients Treated with Stereotactic Body Radiation Therapy (SBRT)

The objective of this study is describe outcome and toxicity for dogs with oral tumors, specifically oral malignant melanoma (OMM), squamous cell carcinoma (SCC), and soft tissue sarcoma (STS) after stereotactic body radiation therapy (SBRT). A single institution retrospective study was conducted. Outcomes were analyzed using Kaplan-Meier analysis and Cox proportional hazard analysis. Treatment responses at different time points were evaluated with Pearson's Chi-squared test to identify prognostic factors. Acute and late toxicities were recorded according to VRTOG criteria and were analyzed to identify risk factors. Adverse events other than acute and late toxicities were recorded. A total of 98 patients met the inclusion criteria (OMM n = 37; SCC n = 18; STS n = 43). The SBRT prescription was 1-6 fractions, with a total dose range of 12-40 Gy. Local progression-free survival (PFS) for OMM, SCC, and STS was 187, 253, and 161 days, respectively. Overall PFS was 152 days and median survival time (MST) was 270 days, with no statistical difference between tumor types. The presence of lymph node metastasis and the use of elective nodal irradiation (ENI) were associated with shorted PFS and MST. Severe acute toxicities to organs at risk affected 10/85 (11.8%) of patients. Osteoradionecrosis and oronasal fistula formation occurred in 23/81 (28.4%) of patients and was significantly associated with tumor type (SCC, P = 0.006). SBRT can be offered as a treatment option for oral tumors in dogs. Toxicities were common and warrant risk factor considerations and adjustments to current SBRT protocols.