Has known central nervous system (ie, brain and/or spinal cord) metastases and/or carcinomatous meningitis.Has a known additional malignancy that is progressing or has required active treatment within the past 3 years.Submit an archival tumor tissue sample or newly obtained core or incisional biopsy of a tumor lesion not previously irradiated for PD-L1 status determination prior to randomization.Has measurable disease per Response Evaluation Criteria in Solid Tumors Version 1.1 (RECIST 1.1) as assessed by the local site investigator/radiology.A female participant is eligible to participate if she is not pregnant or breastfeeding, and at least one of the following conditions applies: is not a woman of childbearing potential (WOCBP) or is a WOCBP who agrees of using a contraceptive method per protocol.Male participants are eligible to participate if they agree to use contraception as per protocol unless confirmed to be azoospermic.Has an Eastern Cooperative Oncology Group (ECOG) performance score (PS) of 0 or 1.Participants who received adjuvant or neoadjuvant therapy are eligible if the adjuvant/neoadjuvant therapy was completed at least 12 months prior to the development of metastatic disease Has not received prior systemic treatment for their metastatic NSCLC.Participants with purely squamous NSCLC do not require testing Has confirmation that epidermal growth factor receptor (EGFR), Anaplastic lymphoma kinase (ALK), or ROS Proto-Oncogene 1, Receptor Tyrosine Kinase (ROS1)-directed therapy is not indicated in nonsquamous NSCLC as well as mixed nonsquamous/squamous NSCLC.Has Stage IV (T any, N any, M1a, M1b, or M1c - American Joint Committee on Cancer 8th Edition) squamous or nonsquamous NSCLC.Has pathologically (histologically or cytologically) confirmed diagnosis of squamous or nonsquamous non-small cell lung cancer (NSCLC).Condition or diseaseД«iological: Pembrolizumab SC Biological: Pembrolizumab IV Drug: Paclitaxel Drug: Nab-Paclitaxel Drug: Carboplatin Drug: Cisplatin Drug: Pemetrexed Participants who discontinue study treatment after receiving the first course of 35 administrations of pembrolizumab (approximately up to 2 years) for reasons other than disease progression or intolerability, may be eligible for a second course of pembrolizumab for up to approximately 1 additional year if they have experienced radiographic disease progression per RECIST 1.1 as assessed by BICR after stopping first course treatment. The primary hypothesis of the study is Pembrolizumab SC is noninferior to pembrolizumab intravenous (IV) for Cycle 1 Area Under Curve (AUC) and Cycle 6 minimal concentration (Ctrough) at steady state. The purpose of this study is to evaluate pembrolizumab (MK-3475) subcutaneous (SC) administration as the first-line therapy in the treatment of metastatic squamous and nonsquamous NSCLC by assessing the pharmacokinetics (PK), safety, and efficacy of pembrolizumab SC injection in combination with standard-of-care chemotherapy. Why Should I Register and Submit Results?.

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