Immunotherapy and Stereotactic Body Radiotherapy (SBRT) for Metastatic Anaplastic Thyroid Cancer

Inclusion Criteria: * Histopathologic confirmation of anaplastic thyroid cancer (or histopathologic report consistent with anaplastic thyroid cancer) at Memorial Sloan Kettering Cancer Center with clinical evidence of metastatic disease not curable by either surgery or radiation therapy * Age ≥ 18 years at time of study entry * ECOG Performance Status of 0-2 * Adequate normal organ and marrow function as defined below: * Hemoglobin ≥ 9.0 g/dL * Absolute neutrophil count (ANC) ≥ 1.5 x 109/L (≥ 1500 per mm\^3) * Platelet count ≥ 100 x 109/L (≥100,000 per mm\^3) * Serum bilirubin ≤ 1.5 x institutional upper limit of normal (ULN). This will not apply to subjects with confirmed Gilbert's syndrome (persistent or recurrent hyperbilirubinaemia that is predominantly unconjugated in the absence of hemolysis or hepatic pathology), who will be allowed only in consultation with their physician * AST (SGOT)/ALT (SGPT) ≤ 2.5 x institutional upper limit of normal unless liver metastases are present, in which case it must be ≤ 5x ULN * Serum creatinine CL\>40 mL/min by the Cockcroft-Gault formula (Cockcroft and Gault 1976) or by 24-hour urine collection for determination of creatinine clearance: * Males: Creatinine CL (mL/min) = Weight (kg) x (140 - Age) . 72 x serum creatinine (mg/dL) °Females: Creatinine CL (mL/min) = Weight (kg) x (140 - Age) x 0.85 72 x serum creatinine (mg/dL) * Female subjects must either be of non-reproductive potential (i.e., post-menopausal by hist…