Lenvatinib and Pembrolizumab for the Treatment of Stage IVB Locally Advanced and Unresectable or Stage IVC Metastatic Anaplastic Thyroid Cancer

This phase II trial studies how well lenvatinib and pembrolizumab work in treating patients with anaplastic thyroid cancer that is stage IVB and has spread to nearby tissue or lymph nodes (locally advanced) and cannot be removed by surgery (unresectable), or stage IVC that has spread to other places in the body (metastatic). Lenvatinib 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. Given lenvatinib and pembrolizumab may work better than giving either one alone in treating stage IVB or C anaplastic thyroid cancer.