Lenvatinib-Associated Erythrocytosis

Abstract

To the Editor:Antiangiogenic receptor tyrosine kinase inhibitors (TKIs) target proangiogenic molecules in tumor microenvironment and induce apoptosis by inhibiting angiogenesis and further tumor proliferation. These are used in the treatment of multiple cancers due to remarkable clinical efficacy. 1 Lenvatinib is a multikinase inhibitor targeting vascular endothelial growth factor receptors 1, 2, and 3; fibroblast growth factor receptors 1-4; plateletderived growth factor a; receptor tyrosine kinase; and rearranged during transfection. 2 This drug has been indicated for the treatment of multiple cancers including advanced renal cell carcinoma, hepatocellular carcinoma, and radioactive iodinerefractory differentiated thyroid carcinomas. Erythrocytosis, as an adverse effect of TKIs, has been reported mostly with sunitinib and sorafenib, rarely with lenvatinib (only 1 case reported). Here, we report 2 more cases of papillary thyroid carcinoma treated with lenvatinib developing significant erythrocytosis. FIGURE 1. Time trend of lenvatinib dosing and hemoglobin (g/dL).