**4. Conclusions**

Recent understanding on the molecular basis of thyroid cancers have led to newer advances in treatment approaches for patients with advanced and recurrent disease. Patients with advanced radioiodine refractory DTC, PDTC were considered to have poor prognoses until recently. The role of cytotoxic chemotherapy in treatment of thyroid cancer is limited. Sorafenib and lenvatinib are approved for advanced

## *Systemic Therapy in Thyroid Cancer DOI: http://dx.doi.org/10.5772/intechopen.106462*

radioiodine refractory and poorly differentiated thyroid cancers and vandetanib and cabozantinib for recurrent or metastatic medullary thyroid cancers. Cabozantinib is also approved for the treatment of locally advanced or metastatic radioactive iodine–refractory differentiated thyroid cancer that has progressed after prior VEGFtargeted therapy. The combination of the BRAF inhibitor, dabrafenib and MEK inhibitor, trametinib, is approved for *BRAF* V600E mutated; unresectable locally advanced anaplastic thyroid cancer. Selpercatinib, RET kinase inhibitor is used for advanced RET mutated medullary thyroid cancers and RET fusion-positive thyroid cancers of any histologic type. Due to the availability of drugs that target specific molecular alterations for the treatment of thyroid cancers, optimal molecular testing to identify suitable candidates for such therapies is warranted. The knowledge of the molecular profile of the tumor allows informed treatment decisions to be made, though optimal therapeutic sequencing of targeted therapy or their combination with immunotherapy is not yet known. More data from ongoing clinical trials might help to document the optimal therapeutic sequencing of available molecular therapies.
