Treatment of a heart base tumor and chylothorax with endovascular stent, stereotactic body radiation therapy, and a tyrosine kinase inhibitor in a dog.

An 8-year-old 28-kg male castrated rough collie was evaluated for persistent chylothorax secondary to right atrial mass. Cardiac ultrasound and computed tomography revealed a right atrial intra- and extraluminal mass with partial obstruction of the cranial vena cava and secondary chylothorax. Vascular stent placement was elected to alleviate cranial vena cava obstruction and secondary chylothorax. An 18 mm × 180 mm self-expanding stent was deployed in the region of the stricture, spanning the cranial vena cava and right atrium. An intrathoracic drainage catheter and subcutaneous port were placed within the right hemithorax, and antiplatelet therapy was initiated. Four weeks later, the dog underwent stereotactic body radiation therapy. Three months following treatment, the dog was diagnosed with supraventricular tachycardia and received antiarrhythmic therapy and antiangiogenic/antiproliferative medication (Palladia™). Subsequent evaluations confirmed the resolution of arrhythmia and pleural effusion. Combined vascular stent placement and stereotactic body radiation therapy for the treatment of a right atrial intraluminal and extraluminal mass leading to cranial vena cava compression and subsequent chylothorax may lead to long-term survival. A good outcome was achieved in this patient due to resolution of pleural effusion, as well as cytoreduction and presumably delayed progression of tumor growth.