VMAT Stereotactic Body Radiation Therapy in a Multimodal Approach to a Carotid Paraganglioma in a Dog.

A 7 yr old female pit bull terrier was presented for a cervical soft tissue swelling located in the left jugular region. No abnormalities were present at physical examination or in the laboratory workup. Computed tomography and MRI scans showed a well-defined, ovoid, single mass in the left dorsal cervical region connected to the common carotid artery, histologically consistent with carotid body paraganglioma. The mass was surgically resected. Frameless stereotactic body radiation therapy with volumetric modulated arc therapy was set up as adjuvant treatment. After radiation therapy, systemic chemotherapy with carboplatin was started. During the first yr of follow-up, acute grade I dermatitis and grade I left-side laryngeal mucositis were recognized. One yr after radiation therapy, no signs of late radiotoxicity or tumor recurrence were observed. Grade I thrombocytopenia concurrent with chemotherapy was observed. This is the first reported case of a carotid body paraganglioma treated by multimodal therapy, with surgical resection and adjuvant radiotherapy and chemotherapy. Stereotactic body radiation therapy with volumetric modulated arc therapy treatment after surgery provided excellent disease control and was well tolerated with slight side effects.