Pembrolizumab After SBRT Versus Pembrolizumab Alone in Advanced NSCLC

The investigators hypothesize that in a significant subset of patients with recurrent NSCLC immunotherapy after SBRT will be superior to treatment with immunotherapy alone and that SBRT, given to a single metastatic site of the tumor, will augment the immune response to the tumor. Objectives: Disease Control Rate (DCR), defined as the percentage of patients having a complete response, partial response or stable disease at 12 weeks, PFS, defined as time from randomization to disease progression or death, OS, defined as time from randomization to death (of any cause). Toxicity.