Part A: Nivolumab Administration. Nivolumab will be given every 2 weeks x 6 at a dose of 240 mg Intravenously (IV) and then every 3 weeks at a dose of 360 mg IV until toxicity, complete response, disease progression, SD at 12 months or a maximum of 96 total weeks (12 weeks induction, 84 weeks maintenance) Patients with disease progression (at any time) or SD at 12 months will be eligible to be considered for participation in Part B of the study.