Tracheoesophageal fistula development following radiotherapy and tyrosine kinase inhibitors in a patient with advanced follicular thyroid carcinoma: a case-based review

Introduction Tracheoesophageal fistulas (TEF) are a rare complication that can occur in patients with radioactive iodine refractory metastatic follicular thyroid carcinoma (FTC) following treatment with radiotherapy (RT) and tyrosine kinase inhibitors (TKI). Methods We describe the case of a TEF development in a 69-year-old male who underwent targeted therapy TKIs and adjuvant RT for radioactive iodine refractory FTC. Results In the case, staging investigations revealed a metastatic, poorly differentiated FTC refractory to radioactive iodine. After 2 years of disease control on Lenvatinib, the patient’s condition progressed, necessitating a switch to Cabozantinib. Soon after, they presented with haemoptysis secondary to invasion of the primary thyroid tumour into the trachea. Radical radiotherapy (45 Gy/30 fractions) was also administered to the thyroid gland, ultimately complicated by radiation necrosis. Four months post-completion of RT and recommencing TKI, the patient presented with haemoptysis and hoarseness secondary to recurrent laryngeal nerve compression and tracheal invasion, as well as dysphagia secondary to oesophageal compression. Following an acute presentation with intractable throat pain, investigations revealed a TEF. Surgical and endoscopic management was deemed inappropriate given the patient’s rapid deterioration and anatomical position of the TEF, and therefore a palliative approach was taken. Conclusion This case report highlights a rare cause of TEF development in a patient having TKI therapy post-RT for advanced FTC. It highlights the importance of monitoring TEF development in this cohort of patients. It demonstrates the importance of patient counselling and education regarding treatment options and the rare side effects of treatments.