Pembrolizumab Every 12 Weeks Versus Every 3 Weeks in Treating Patients With Non-small Cell Lung Cancer

PRIMARY OBJECTIVES: I. To evaluate the 1-year progression-free survival rate with 200mg pembrolizumab administered every 3 weeks compared to 200mg pembrolizumab administered every 12 weeks. SECONDARY OBJECTIVES: I. To assess overall survival between the two treatment groups. II. To assess the serious adverse event profiles between the two treatment groups. EXPLORATORY OBJECTIVES: I. To evaluate circulating biomarkers of treatment response and resistance. II. To characterize fecal microbiotic profile and to correlate those results with tumor characteristics and antitumor immune responses. OUTLINE: Patients are randomized to 1 of 2 arms. ARM I: Patients receive pembrolizumab intravenously (IV) over 30 minutes every 3 weeks for up to 24 months in the absence of disease progression or unacceptable toxicity. ARM II: Patients receive pembrolizumab IV over 30 minutes every 12 weeks for up to 24 months in the absence of disease progression or unacceptable toxicity. After completion of study treatment, patients are followed up at 30 days, and then every 12 weeks for at least 12 months.