Study of Targeted Therapy vs. Chemotherapy in Patients With Thyroid Cancer

This phase III trial compares the effect of cabozantinib versus combination dabrafenib and trametinib for the treatment of patients with differentiated thyroid cancer that does not respond to treatment (refractory) and which expresses a BRAF V600E mutation. Cabozantinib is in a class of medications called receptor tyrosine kinase inhibitors. It binds to and blocks the action of several enzymes which are often over-expressed in a variety of tumor cell types. This may help stop or slow the growth of tumor cells and blood vessels the tumor needs to survive. Dabrafenib is an enzyme inhibitor that binds to and inhibits the activity of a protein called B-raf, which may inhibit the proliferation of tumor cells which contain a mutated BRAF gene. Trametinib is also an enzyme inhibitor. It binds to and inhibits the activity of proteins called MEK 1 and 2, which play a key role in activating pathways that regulate cell growth. This may inhibit the growth of tumor cells mediated by these pathways. The usual approach for patients with thyroid cancer is targeted therapy with dabrafenib and trametinib. This trial may help researchers decide which treatment option (cabozantinib alone or dabrafenib in combination with trametinib) is safer and/or more effective in treating patients with refractory BRAF V600E-mutated differentiated thyroid cancer.