The Management of Medullary Thyroid Carcinoma in the Era of Targeted Therapy

Medullary thyroid cancer (MTC) is a rare cancer comprising approximately 5% of all thyroid cancers. The majority arises sporadically but around 25% are hereditary forming part of the Multiple Endocrine Neoplasia (MEN) type 2 syndromes. The initial management is surgical, the extent of resection determined by radiological stage, presence of and specific REarranged during Transfection (RET) oncogene mutation and level of serum calcitonin. External beam radiotherapy may be utilised in the adjuvant setting to improve local control rates. Conventional cytotoxic agents remain essentially futile in the management of advanced MTC with response rates of around 15-20% at best. Over the last decade, alongside a greater understanding of the molecular pathogenesis of MTC we have seen the development of small molecule agents including tyrosine kinase inhibitors targeting vascular endothelial growth factor receptors (VEGFRs) and RET with activity in advanced MTC. This review will examine the evidence for this therapeutic approach, when to consider initiating and how to manage toxicities arising from such therapies in the treatment of advanced MTC.