Medullary Thyroid Cancer in the Era of Tyrosine Kinase Inhibitors: To Treat or Not to Treat-and With Which Drug-Those Are the Questions

Context: Medullary thyroid cancer (MTC) is a rare form of thyroid cancer comprising approximately 4% of all thyroid cancers. The majority of patients have a relatively good prognosis; however, a subgroup of patients will require systemic therapy. Large phase III randomized trials led to the approval of two drugs-vandetanib and cabozantinib-for progressive or symptomatic MTC. The decision regarding which drug to initiate first is not entirely clearandis a common concern amongst treating physicians. Evidence Acquisition and Synthesis: A review of the literature in English was conducted, and data were summarized and integrated into a decision matrix. Conclusions: The decision regarding which drug to initiate first for progressive MTC should be based on a careful review of the medical history, physical examination findings, medication list, electrocardiogram, laboratory results, and tumor characteristics. It is necessary to consider the relative contra-indications when choosing which drug to initiate first.