Aerodigestive fistula formation as a rare side effect of antiangiogenic tyrosine kinase inhibitor therapy for thyroid cancer

Background: In the past decade, targeted therapy with antiangiogenic drugs has become standard of care for most types of metastatic, progressive thyroid cancer. While these drugs were thought initially to be less toxic than traditional chemotherapy, they can have rare but serious and fatal toxicities. Once such toxicity that has been reported in other tumor types is upper airway fistula formation, which can be life-threatening. Summary: Here, we describe three patients treated with antiangiogenic tyrosine kinase inhibitors at two academic institutions who developed aerodigestive fistula. All three patients had risk factors for fistula formation, which included external beam radiation and/or large tumor with invasion of the tracheal wall. Conclusions: Fistula formation is a known but rare side effect of antiangiogenic tyrosine kinase inhibitors. Knowledge of the risk factors that may predispose thyroid cancer patients to this serious adverse event is vital prior to prescribing antiangiogenics. Particular caution should be observed when using these drugs in patients undergoing radiation therapy or surgery, or in patients whose tumor is invading vital structures of the neck, as they may be at higher risk of developing this rare complication. In these patients, antiangiogenic tyrosine kinase inhibitors should be used cautiously, patients should be aware of the risk, and physicians should monitor patients for symptoms of fistula.