Hypofractionated radiotherapy for a feline tracheal epithelial tumour

Abstract

Case summary An 8-year-old spayed female Ragdoll cat presented with a several-month history of coughing and exertional dyspnoea. Initial treatment for presumed feline asthma was unsuccessful. Thoracic CT revealed an intraluminal mass at the carina and complete atelectasis of the right middle lung lobe. Endoscopy initially identified an intraluminal mass. As biopsy was considered unsafe owing to the risk of acute airway obstruction, brush cytology was performed instead; however, it was non-diagnostic. As a result of progressive obstructive respiratory failure, urgent palliative radiation therapy was initiated (6 Gy × 6 fractions weekly; total dose 36 Gy). By the fourth fraction, the cat showed marked clinical improvement, and imaging confirmed tumour shrinkage. Before the fifth fraction, endoscopic biopsies were repeated and histopathology established a diagnosis of an epithelial malignant tumour, most consistent with adenocarcinoma. Toceranib phosphate was introduced on an alternate-day schedule as adjuvant therapy. The short-term outcome was favourable, with resolution of clinical signs. The cat remained clinically well more than 150 days after the start of radiation therapy. Relevance and novel information Primary tracheal tumours are rare in cats, and treatment protocols are not well defined. Surgical excision of masses involving the carina is technically challenging, and radiation therapy for this location has not previously been reported. In this case, a short course of hypofractionated radiation therapy rapidly alleviated airway obstruction, allowing stabilisation of ventilation and subsequent histopathological confirmation. This staged diagnostic–therapeutic approach highlights the utility of hypofractionated radiation therapy as an emergency airway-sparing treatment for cats with obstructive tracheal tumours.