Immunotherapy With or Without SBRT in Patients With Stage IV Non-small Cell Lung Cancer

PRIMARY OBJECTIVES: I. To compare progression-free survival of patients randomized to radiation and consolidative immunotherapy against those receiving consolidative immunotherapy alone. SECONDARY OBJECTIVES: I. To estimate overall survival in all patients and will compare overall survival of those randomized to radiation and consolidative immunotherapy against those receiving consolidative immunotherapy alone. II. In patients receiving radiation, to describe the rate of in-field local control and rate of out-of-field disease progression with serial imaging. III. In patients not receiving radiation, describe progression at known sites of disease after first line systemic therapy and rate of development of new metastases with serial imaging. IV. To evaluate toxicity associated with radiation followed by consolidative immunotherapy. OUTLINE: Patients are randomized to 1 of 2 arms. ARM I: Patients undergo 3-10 treatments of stereotactic body radiation therapy (SBRT). Patients also receive pembrolizumab intravenously (IV) over 30 minutes every 3-4 weeks for 1 year at the discretion of the treating physician. ARM II: Patients receive pembrolizumab IV over 30 minutes every 3-4 weeks for 1 year at the discretion of the treating physician. After completion of study treatment, patients are followed up at 1 month, every 3 months for 1 year, every 6 months for the next 2 years, and then annually for 2 years.