The goal of this non-interventional study is to emulate the KEYNOTE-189 randomized controlled trial of pembrolizumab for the treatment of metastatic non-small cell lung cancer using real-world, electronic health record data. The main questions this study aims to answer are:

1. Do patients with metastatic non-small cell lung cancer (NSCLC) treated with pemetrexed, cisplatin/carboplatin, and pembrolizumab have improved real-world overall survival (rwOS) and real-world progression-free survival (rwPFS) compared with patients treated with pemetrexed and cisplatin/carboplatin alone?
2. How do the results of this non-interventional study compare to those of the KEYNOTE-189 randomized controlled trial?

The Coalition to Advance Real-World Evidence through Randomized Controlled Trial Emulation (CARE) Initiative is a program designed to build an empirical evidence base for the use of real-world data (RWD) in clinical and regulatory decision-making. Using randomized controlled trials (RCTs) as a benchmark for causal effect estimates, a series of RCT emulations will be conducted across varying trials, real world data sources, and study design elements to better understand under what conditions non-interventional studies, using data generated during routine clinical care, can provide reliable conclusions about drug effectiveness.

In this study, real-world electronic health record (EHR) data will be used to emulate the KEYNOTE-189 efficacy trial of pembrolizumab as first-line therapy in patients with metastatic non-small cell lung cancer (NSCLC) without epidermal growth factor receptor (EGFR) or anaplastic lymphoma kinase (ALK) sensitizing mutations. Similarly to the KEYNOTE-189 trial, this study will compare real-world overall survival (rwOS) and real-world progression-free survival (rwPFS) between patients who initiate pemetrexed, platinum-based chemotherapy, and pembrolizumab, and patients who initiate pemetrexed and platinum-based chemotherapy alone.

Inclusion Criteria:

• Non-small cell lung cancer (NSCLC) diagnosis
• Histology not indicative of squamous cell carcinoma
• Metastatic disease
• Epidermal growth factor receptor (EGFR) and Anaplastic lymphoma kinase (ALK)-negative or Kirsten rat sarcoma viral oncogene homolog (KRAS)-positive
• No prior systemic treatment for metastatic NSCLC
• No record of adjuvant or neoadjuvant therapy in the 12 months before metastatic diagnosis
• Eastern Cooperative Oncology Group (ECOG) performance status of 0, 1, or missing or Karnofsky performance status >=70 or missing
• No lab results indicating inadequate organ function, as defined in the KEYNOTE-189 RCT protocol

Exclusion Criteria:

• Histology indicative of squamous cell carcinoma or small cell elements
• Prior systemic treatment for metastatic NSCLC
• Prior antineoplastic biological therapy
• History of major cancer-related surgery in the 3 weeks before study drug initiation
• Radiation therapy to the lung >30 Gy in the 6 months before study drug initiation
• Prior diagnosis of clinically active diverticulitis, intra-abdominal abscess, or gastrointestinal obstruction
• Diagnosis of a second primary malignant neoplasm
• Diagnosis of brain, central nervous system, and/or spinal cord metastases
• Diagnosis of autoimmune disease and treatment with corticosteroids or immunosuppressive drugs after diagnosis and within the 2 years prior to study drug initiation
• Treatment with a non-topical systemic steroid in each of the 6 months prior to study drug initiation
• Prior treatment with pembrolizumab or any other anti-PD-1, PD-L1, PD-L2 agent or an antibody targeting other immuno-regulatory receptors or mechanisms
• Treatment with non-topical antibiotics, antifungals, or antivirals within 2 weeks after an infection diagnosis in the month prior to study drug initiation
• Diagnosis of human immunodeficiency virus infection
• Diagnosis of acute hepatitis B or C
• Diagnosis of ascites or plural effusion in the 3 months prior to study drug initiation
• Prior diagnosis of interstitial lung disease or diagnosis of pneumonitis and record of treatment with glucocorticoids within 30 days

Patients identified in the electronic health record data source with metastatic EGFR/ALK-negative non-small cell lung cancer initiating treatment with the study drugs (pemetrexed, cisplatin/carboplatin, pembrolizumab)