There are no genders or racial restrictions. 8.1 PRETREATMENT EVALUATION To be completed within 45 days prior to starting avelumab unless otherwise s p e c i f i e d : 1. Signed informed consent for study participation 2. FDG-PET scan 3. CT of the chest, abdomen, and pelvis, preferably with contrast. The companion CT scan from the above FDG -PET scan may fulfill this requirement. 4. MRI of the lesion to be irradiated according to the following guidelines in the MSKCC Department of Radiation Oncology a. Contraindication to MRI (i.e. pacemaker) = no participation in MRI component. b. Contraindication to contrast only = MRI w/o contrast c. No contraindication = MRI with contrast 5. 12-lead Electrocardiogram (EKG) 6. History and physical examination, including height, weight, vital signs (temperature, pulse rate, respiration rate, blood pressure), and performance status ( Karnofsky) 7. Serum or urine pregnancy test for all women of childbearing potential (serum pregnancy test within 14 days or urine pregnancy test within 24 hours of starting avelumab) 8. CBC with differential and platelet count, CMP (including Na, Cl, BUN, Creatinine, K, CO2, glucose, AST, ALT, alkaline phosphatase, total bilirubin, calcium, albumin, and total protein) 9. Free T4 and TSH 10. Serology for HEP BsAg, HBcAb and hepatitis C antibody within 30 days prior to starting avelumab 11. Baseline blood test for research purposes (See Section 1 0 .