 Patients receive durvalumab intravenously IV over 60 minutes and tremelimumab IV over 60 minutes on day 1. Treatment repeats every 4 weeks for up to 4 courses in the absence of disease progression or unacceptable toxicity. Beginning at week 17, patients receive durvalumab IV over 60 minutes on day 1. Treatment repeats every 4 weeks for up to 9 courses in the absence of disease progression or unacceptable toxicity. 