Vandetanib (ZD6474, Caprelsa, AstraZeneca), an oral small-molecule tyrosine kinase inhibitor (TKI) that targets the rearranged during transfection receptor (RET), VEGF receptor (VEGFR2-3), and EGF receptor (EGFR), is the first systemic therapy approved by the U.S. Food and Drug Administration (FDA) for the treatment of symptomatic or progressive advanced medullary thyroid cancer (MTC). In a randomized phase III trial of patients with unresectable, locally advanced, or metastatic MTC, vandetanib improved progression-free survival compared with placebo [HR, 0.46; 95% confidence interval (CI), 0.31-0.69; P < 0.001]. However, the benefits in delaying disease progression need to be balanced against the associated and potentially serious toxicities, including diarrhea, hypertension, and QTc prolongation. Here, we review the clinical development of vandetanib leading to its integration into the current treatment paradigm and highlight the ongoing and future challenges in TKI use in MTC.