Patients will be randomized in a 2:1:1 ratio to MEDI4736 + tremelimumab combination therapy, MEDI4736 monotherapy, or SoC. Patients in all arms will continue therapy until progression. Tumor assessments will be performed on computed tomography scans or magnetic resonance imaging scans, preferably with intravenous (IV) contrast. Efficacy for all patients will be assessed by objective tumor assessments every 6 weeks for the first 24 weeks, then every 8 weeks thereafter until treatment discontinuation due to progression or toxicity. All patients will be followed every 3 months for survival after progression is confirmed.