Phase II clinical trial of sorafenib in metastatic medullary thyroid cancer.

Purpose: Mutations in the RET proto-oncogene and vascular endothelial growth factor receptor (VEGFR) activity are critical in the pathogenesis of medullary thyroid cancer (MTC). Sorafenib, a multikinase inhibitor targeting Ret and VEGFR, showed antitumor activity in preclinical studies of MTC.

Patients And Methods: In this phase II trial of sorafenib in patients with advanced MTC, the primary end point was objective response. Secondary end points included toxicity assessment and response correlation with tumor markers, functional imaging, and RET mutations. Using a two-stage design, 16 or 25 patients were to be enrolled onto arms A (hereditary) and B (sporadic). Patients received sorafenib 400 mg orally twice daily.

Results: Of 16 patients treated in arm B, one achieved partial response (PR; 6.3%; 95% CI, 0.2% to 30.2%), 14 had stable disease (SD; 87.5%; 95% CI, 61.7% to 99.5%), and one was nonevaluable. In a post hoc analysis of 10 arm B patients with progressive disease (PD) before study, one patient had PR of 21+ months, four patients had SD >or= 15 months, four patients had SD
Conclusion: Sorafenib is reasonably well tolerated, with suggestion of clinical benefit for patients with sporadic MTC. Caution should be taken because of the rare but fatal toxicity potentially associated with sorafenib.