A Study of Pembrolizumab (MK-3475) With or Without Lenvatinib (E7080/MK-7902) as First Line (1L) Intervention in a Programmed Cell Death-ligand 1 (PD-L1) Selected Population With Recurrent or Metastatic Head and Neck Squamous Cell Carcinoma (R/M HNSCC) (MK-7902-010/LEAP-010)-China Extension

This is a study of pembrolizumab (MK-3475) with or without lenvatinib (E7080/MK-7902) as a first line intervention in a PD-L1 selected population with participants with recurrent or metastatic head and neck squamous cell carcinoma. Hypotheses include: * Pembrolizumab + lenvatinib is superior to pembrolizumab + placebo with respect to Objective Response Rate (ORR) per Response Evaluation Criteria in Solid Tumors Version 1.1 (RECIST 1.1) by blinded independent central review (BICR). * Pembrolizumab + lenvatinib is superior to pembrolizumab + placebo with respect to Progression Free Survival (PFS) per RECIST 1.1 as assessed by BICR. * Pembrolizumab + lenvatinib is superior to pembrolizumab + placebo with respect to overall survival (OS).