Sorafenib and Sunitinib for the Treatment of Metastatic Thyroid Cancer of Follicular Origin: A 7-Year Single-Centre Experience.

Background: Radioactive iodine (RAI)-refractory differentiated thyroid cancer (DTC) is a rare form of DTC which poses a therapeutic challenge due to the scarcity of effective treatment options. In recent years several tyrosine kinase inhibitors targeting specific molecular pathways involved in its pathogenesis have been investigated, such as sorafenib, lenvatinib, and sunitinib. These appear to be associated with improved progression-free survival (PFS).

Objectives: We aim to describe our experience with sorafenib and sunitinib in the treatment of RAI-refractory metastatic DTC and to evaluate and compare their efficacy and adverse effect profiles.

Method: A total of 28 patients with RAI-refractory metastatic DTC were included - 26 had first-line treatment with sorafenib (8 subsequently switched to sunitinib, most due to disease progression) and 2 with sunitinib. We evaluated PFS and best radiological response achieved with each agent as primary endpoints. The secondary objective was to describe adverse effects and safety profile.

Results: Mean PFS was 10.8 months with sorafenib and 6 months with sunitinib as a second-line treatment. Best overall response was partial remission (PR) with either agent - PR rate of 30.7% with sorafenib and 37.5% with second-line sunitinib. All treatment courses had registered adverse effects and 13.9% justified definitive treatment cessation.

Conclusions: Sorafenib and sunitinib appear to be effective treatment options in delaying disease progression of patients with RAI-refractory metastatic DTC, with an acceptable safety profile. Interestingly, sunitinib appears to show some efficacy even in patients who experience disease progression on sorafenib.