Multitargeted Kinase Inhibition in Metastatic Differentiated Radioiodine-Refractory Thyroid Cancer: A Look at New Therapeutic Options for a Rare Disease

<b><i>Background:</i></b> Metastatic differentiated thyroid cancer (DTC) is a rare disease that is in the first line treated with iodine-131 radioisotope therapy. Until recently, options were very limited in the case of progressive radioactive-iodine (RAI)-refractory disease. Based on new study results, tyrosine kinase inhibitors (TKIs) have attracted attention. The TKI sorafenib demonstrated significantly improved progression-free survival (PFS) in a phase III trial. Recent data from another phase III trial showed that the TKI lenvatinib achieved high response rates and a large improvement in PFS in metastatic RAI-refractory DTC patients in the first-line setting and after 1 prior line of TKI. However, little is known about the response to lenvatinib in patients pretreated with multiple lines of TKIs. <b><i>Case Report:</i></b> We present the case of a 45-year-old man with metastatic RAI-refractory DTC progressing after multiple prior treatments with TKIs and chemotherapy. A very good and long-lasting response to lenvatinib was observed. Careful and prospective monitoring as well as management of side effects including dose adaptation were necessary to ensure success of treatment. <b><i>Conclusion:</i></b> Here, we review different novel treatment options for patients with metastatic RAI-refractory DTC.