Purpose

This phase II trial studies the effect of pembrolizumab, dabrafenib, and trametinib before surgery in treating patients with BRAF V600E-mutated anaplastic thyroid cancer. BRAF V600E is a specific mutation (change) in the BRAF gene, which makes a protein that is involved in sending signals in cells and in cell growth. It may increase the growth and spread of tumor cells. Dabrafenib and trametinib may stop the growth of tumor cells by blocking some of the enzymes needed for cell growth. Immunotherapy with monoclonal antibodies, such as pembrolizumab, may help the body's immune system attack the cancer, and may interfere with the ability of tumor cells to grow and spread. Pembrolizumab, dabrafenib, and trametinib may help to control BRAF V600E-mutated anaplastic thyroid cancer when given before surgery.