Safety and Efficacy Study of Pemetrexed + Platinum Chemotherapy + Pembrolizumab (MK-3475) With or Without Lenvatinib (MK-7902/E7080) as First-line Intervention in Adults With Metastatic Nonsquamous Non-small Cell Lung Cancer (MK-7902-006/E7080-G000-315/LEAP-006)-China Extension Study

The purpose of this study is to assess the safety and efficacy of pemetrexed+platinum chemotherapy+pembrolizumab (MK-3475) with or without lenvatinib (MK-7902/E7080) as first-line intervention in adults from mainland China with metastatic nonsquamous non-small cell lung cancer. The primary study hypotheses state that: 1) the combination of lenvatinib+platinum doublet chemotherapy+pembrolizumab prolongs Progression-free Survival (PFS) as assessed by blinded independent central review (BICR) per modified Response Evaluation Criteria in Solid Tumors version 1.1 (RESIST 1.1) compared to matching placebo+platinum doublet chemotherapy+pembrolizumab, and 2) the combination of lenvatinib+platinum doublet chemotherapy+pembrolizumab prolongs Overall Survival (OS) compared to matching placebo+platinum doublet chemotherapy + pembrolizumab.