Beneficial effects of sorafenib on tumor progression, but not on radioiodine uptake, in patients with differentiated thyroid carcinoma

Objective Treatment options for patients with radioactive iodine (RaI) refractory metastases of differentiated thyroid carcinoma (DTC) are limited. We studied the effects of the multitarget tyrosine kinase inhibitor sorafenib on the reinduction of RaI uptake and tumor progression. Design: Open, single center, single arm 26-week prospective phase II study with open-ended extension. Methods: We treated 31 patients with progressive metastatic or locally advanced RaI refractory DTC with sorafenib 400 mg b.i.d. The primary endpoint was reinduction of RaI uptake at 26 weeks. Additional endpoints were the radiological response and the influence of bone metastases. Results: At 26 weeks of sorafenib therapy, no reinduction of RaI uptake at metastatic sites was observed, but 19 patients (59%) had a clinical beneficial response, eight of whom had a partial response (25%) and 11 had stable disease (34%) Seven patients had progressive disease (22%). Sorafenib was significantly less effective in patients with bone metastases The estimated median progression free survival was 58 weeks (95% confidence interval, CI. 47-68). In general, thyroglobulin (Tg) response (both unstimulated and TSH stimulated) reflected radiological responses The median time of the nadir of Tg levels was 3 months. Responses were not influenced by histological subtype, mutational status or other variables. No unusual side effects were observed. Conclusions: Sorafenib has a beneficial effect on tumor progression in patients with metastatic DTC, but was less effective in patients with bone metastases. Diagnostic whole body scintigraphy did not reveal an effect of sorafenib on the reinduction of RaI uptake.