Efficacy of lenvatinib in treating thyroid cancer.

INTRODUCTION: Radioiodine [RAI]-resistant advanced and progressive differentiated thyroid cancer [DTC], although rare, constitutes a real challenge as its prognosis is poor and available therapeutic options, until now, have been limited. Discovery of a crucial role of distinct tyrosine kinases in DTC pathogenesis opened up new options in systemic treatment. Lenvatinib is an oral potent multi kinase inhibitor [MKI] of different growth factor receptors including VEGFR1/Flt-1, VEGFR2/KDR, VEGFR3, FGFR1,2,3,4, PDGFR-β as well as RET and KIT signaling networks. Its activity against RAI-refractory DTC was demonstrated in clinical studies fulfilling evidence-based medicine [EBM] criteria. The drug showed acceptable tolerance and manageable toxicity. AREAS COVERED: published results of phase II and III studies and other reports evaluated the efficacy and safety of lenvatinib in DTC and in medullary thyroid carcinoma. EXPERT OPINION: Currently there are two different MKIs, lenvatinib and sorafenib, which have demonstrated effectiveness against RAI-refractory DTC. However, to date, the question of which drug should be chosen for first line treatment remains open. The other question: when to start the treatment seems to be no less important. Whether disease progression, even by RECIST, is enough to initiate a therapy or tumor burden also plays an important role? EBM study, to resolve these issues, is our task for the nearest future.