Long-term remission in a cat with laryngeal squamous cell carcinoma treated with stereotactic radiation therapy

Case summary: A 14-year-old spayed female domestic shorthair cat was referred for evaluation of a laryngeal mass. The cat had a 2-month history of stridor and hoarseness, without any reported decrease in appetite. Laryngeal ultrasonography, fluoroscopy, endoscopy and contrast-enhanced CT revealed a 1.7 cm laryngeal mass without metastasis. A biopsy obtained under laryngoscopic guidance confirmed squamous cell carcinoma (SCC). The cat underwent stereotactic radiation therapy (SRT) in three 10 Gy fractions on consecutive days (total 30 Gy). Mild drooling occurred during treatment and was controlled with prednisolone. A partial response was achieved 45 days after SRT, with improvement in presenting signs. The cat maintained remission without late adverse effects until day 520; however, progressive disease was evident on day 603, and the cat died on day 644. Relevance and novel information: Feline laryngeal SCC is rare, carries a poor prognosis and lacks established treatment protocols. Traditional surgery, such as laryngotomy with or without tracheostomy, often leads to severe or fatal complications. Evidence on radiation therapy in this tumour type is limited. To the authors' knowledge, this is the first report of long-term remission in a cat with laryngeal SCC treated with SRT.