A retrospective analysis of stereotactic body radiation therapy for canine heart base tumors: 26 cases

Abstract Introduction This study retrospectively evaluated outcomes and adverse radiation effects (ARE) associated with stereotactic body radiation therapy (SBRT) for canine heart base tumors (HBT). A secondary aim was to identify any demographic or echocardiographic factors that might determine which dogs would most benefit from SBRT. Animals Twenty-six dogs that received SBRT for an imaging-based diagnosis of a HBT were evaluated. Methods Twenty-three dogs were treated with three fractions of 10 Gy delivered daily or every other day. The remaining 3 dogs received variable protocols of one to five fractions. Demographic, echocardiographic, and radiographic information, adverse radiation effects (ARE), and treatment responses were collected. Correlations of this data with survival time were evaluated. Results Median overall survival time was 404 days (95% CI 239-554 days). The majority of dogs experienced a partial response (25%) or stable disease (60%) for a median duration of 333 days (95% CI 94 to 526 days). Three dogs had progressive disease within six months of SBRT. Radiographic pneumonitis was identified in 7/23 dogs and clinical pneumonitis was identified in 4 dogs. No other AREs were noted. The rate of distant metastasis was 13%. Vena caval obstruction, supraventricular and ventricular arrhythmias, clinical signs, and enlarged locoregional lymph nodes at presentation were negatively associated with survival time on multivariate analysis. Conclusions SBRT was delivered with a low rate and degree of normal tissue complications. Asymptomatic dogs with confirmed, progressive growth of a HBT may most likely benefit from SBRT.