A Phase 3, Randomized, Placebo-Controlled Clinical Study to Evaluate the Safety and Efficacy of Stereotactic Body Radiotherapy (SBRT) With or Without Pembrolizumab (MK-3475) in Participants With Medically Inoperable Stages I or IIA Non Small Cell Lung Cancer (NSCLC) (KEYNOTE-867)

The purpose of this study is to assess the efficacy and safety of stereotactic body radiotherapy (SBRT) plus pembrolizumab (MK-3475) in the treatment of adult participants with medically inoperable Stage I or IIA non-small cell lung cancer (NSCLC).

The primary study hypotheses are:

1. SBRT plus pembrolizumab prolongs Event-free Survival (EFS) compared to SBRT plus placebo (normal saline solution), and
2. SBRT plus pembrolizumab prolongs Overall Survival (OS) compared to SBRT plus placebo.