Sequential TKI treatments for iodine-refractory differentiated thyroid carcinomas.

Abstract

6092 Background: Tyrosine kinase inhibitors (TKI) are currently used to treat patients with advanced iodine-refractory differentiated thyroid cancers (DTC) but none has been approved by the FDA or the EMA until now. Sometimes, patients are treated with off-label TKI when a clinical trial is not available or in second- and third-line therapy. Methods: We hereby report the efficacy of “off-label” sorafenib and sunitinib treatments as first-, second- and third-line therapy in metastatic DTC patients from the French TUTHYREF (TUmeurs THYroïdiennes REFractaires) network. Primary endpoints were progression free survival (PFS) and tumor response according to sequential TKI treatment. Secondary endpoint was organ-specific metastatic site analysis. Results: 45 patients with advanced iodine-refractory DTC treated with off-label TKI were included in this study (26 men, mean age: 62 years). 22 had papillary, 10 had follicular and 13 had poorly DTC. 24/45 patients were treated with two and 3/45 with three lines of TKIs. Sorafenib was the most frequently used (57%) followed by sunitinib (21.5%) and vandetanib (21.5%). Partial response (PR) rate was of 29% in the 21 patients who received first-line sorafenib therapy whereas PR was observed in 57% of the 7 first-line sunitinib patients. There was no PR with second- (n=24) and third-line (n=3) treatments. However, median progression free survival (PFS) was similar in second- as compared to first-line sorafenib or sunitinib treatment (6.7 vs. 7.6 months, HR 0.85 (95CI 0.45-1.61) p=0.6). Liver metastases were the most responsive to treatment (n=7; mean of -30%), followed by lung (n=57; mean of -19%) and lymph node (n=43; mean of -13%) metastases. Bone (n=14) and pleural (n=9) lesions were the most refractory to treatment (mean of -1% and -5%, respectively). Conclusions: Due to the small number of patients, we could not recommend a specific treatment sequence (sorafenib then sunitinib) over another (sunitinib then sorafenib). But TKI therapy appears to be beneficial in refractory DTC patients even in second- and third-line therapy, with similar PFS and stable disease as best response. Bone and pleural metastases were the most refractory and liver lesions the most responsive to treatment.