Stereotactic body radiation therapy as an alternative to adrenalectomy for the treatment of pheochromocytomas in 8 dogs

Abstract The objective of this report is to describe the use and outcome of stereotactic body radiation therapy (SBRT) for treatment of pheochromocytomas in 8 dogs. Pheochromocytomas are an uncommon but challenging tumour to manage. Adrenalectomy is the standard of care for treatment of pheochromocytomas in both animals and humans; however, unpredictable catecholamine secretion from the tumour and vascular and local invasion of the tumour and thrombi can pose life‐threatening perioperative and anaesthetic risks. SBRT has been investigated as an alternative to adrenalectomy in human patients with pheochromocytomas. Eight dogs with clinical signs, an adrenal mass, and cytology and/or urine normetanephrine/creatinine ratios consistent with pheochromocytoma were treated with SBRT in lieu of adrenalectomy. Three dogs presented with acute hemoabdomen. Seven dogs had caval tumour invasion, 3 with extension into the right atrium. Following SBRT, all dogs had complete resolution of clinical signs and reduced urine normetanephrine/creatinine ratio and/or tumour size. No significant anaesthetic complications were encountered. Acute radiation toxicity was limited to grade I gastrointestinal signs in 3 dogs and resolved within 1–2 days of symptomatic therapy. Five of 8 dogs were alive at the time of follow up, with a median follow up time of 25.8 months. SBRT resulted in a favourable outcome and mitigated the life‐threatening risks of adrenalectomy in these 8 dogs. SBRT may be a safe and effective alternative to adrenalectomy for pheochromocytomas in dogs with non‐resectable tumours, or for owners averse to the risks of surgery.