A Study Using Regorafenib as Second or Third Line Therapy in Metastatic Medullary Thyroid Cancer

Inclusion Criteria: * Subjects must be able to understand and be willing to sign the written informed consent form. A signed informed consent form must be appropriately obtained prior to the conduct of any trial-specific procedure. * Age ≥ 18 years. * Life expectancy of at least 12 weeks (3 months). * Eastern Cooperative Oncology Group performance status of ≤1. * Histologically or cytologically confirmed diagnosis of metastatic medullary thyroid cancer. * Documented disease progression within 6 months prior to study registration, as defined by RECIST criteria. * Must have at least 1 site of measurable disease by RECIST criteria, by version 1.1. * Archival tissue block or unstained slides (from primary or metastatic site) must be available, otherwise fresh tissue biopsy sample will be collected. * Any number of prior chemotherapies and targeted therapies are allowed. * Patients must have received at least one prior line of targeted therapy. * Adequate bone marrow, liver and renal function as assessed by the following laboratory requirements within 3 weeks prior to study registration: * Total bilirubin ≤ 1.5 x the upper limits of normal (ULN) * Alanine aminotransferase (ALT) and aspartate amino-transferease (AST) ≤ 2.5 x ULN (≤ 5 x ULN for subjects with liver involvement of their cancer) * Alkaline phosphastase limit ≤ 2.5 x ULN (≤ 5 x ULN for subjects with liver involvement of their cancer) * Serum creatinine ≤ 1.5 x the ULN * International normalized ratio (INR)/ …