SUMMARY: The American Cancer Society estimates that for 2021, about 235,760 new cases of lung cancer will be diagnosed and 131,880 patients will die of the disease. Lung cancer is the leading cause of cancer-related mortality in the United States. Non-Small Cell Lung Cancer (NSCLC) accounts for approximately 85% of all lung cancers. Of the three main subtypes of NSCLC, 30% are Squamous Cell Carcinomas (SCC), 40% are Adenocarcinomas and 10% are Large Cell Carcinomas.
Immunotherapy with Immune Checkpoint Inhibitors (ICIs) has revolutionized cancer care and has become one of the most effective treatment options, by improving Overall Response Rate and prolongation of survival across multiple tumor types. Immune Checkpoint Inhibitors (ICIs) target Programmed cell Death protein-1 (PD-1) receptors on T cells, as well as Programmed cell Death Ligand-1 (PD-L1), PD-L2 and Cytotoxic T-Lymphocyte-Associated protein-4 (CTLA-4), and many other important regulators of the immune system, which are upregulated in some tumor types. T-cell proliferation and cytokine production is inhibited upon binding of the PD-1 ligands PD-L1 and PD-L2, to the PD-1 receptor found on T cells.
KEYTRUDA® (Pembrolizumab) is a fully humanized, Immunoglobulin G4, anti-PD-1, monoclonal antibody, that binds to the PD-1 receptor and blocks its interaction with ligands PD-L1 and PD-L2, releasing PD-1 pathway-mediated inhibition of the immune response. Unleashing the T cells results in T cell proliferation, activation and a therapeutic response. High level of PD-L1 expression is defined as membranous PD-L1 expression on at least 50% of the tumor cells, regardless of the staining intensity. It is estimated that based on observations from previous studies, approximately 25% of the patients with advanced NSCLC have a high level of PD-L1 expression, and high level of PD-L1 expression has been associated with significantly increased response rates to KEYTRUDA®.
KEYNOTE-024 is an open-label, randomized, Phase III trial in which KEYTRUDA® administered at a fixed dose was compared with investigator’s choice of cytotoxic chemotherapy, as first line therapy, for patients with advanced NSCLC, with tumor PD-L1 expression of 50% or greater. Three hundred and five (N=305) treatment naïve patients with advanced NSCLC and PD-L1 expression on at least 50% of tumor cells, were randomly assigned in a 1:1 ratio to receive either KEYTRUDA® (N=154) or chemotherapy (N=151). Enrolled patients had no sensitizing EGFR mutations or ALK translocations. Treatment consisted of KEYTRUDA® administered at a fixed dose of 200 mg IV every 3 weeks for up to 2 years or the investigator’s choice of Platinum-based chemotherapy for 4-6 cycles. Pemetrexed (ALIMTA®) based therapy was permitted only for patients who had non-squamous tumors and these patients could receive ALIMTA® maintenance therapy after the completion of combination chemotherapy. Patients in the chemotherapy group who experienced disease progression were allowed to cross over to the KEYTRUDA® group. The Primary end point was Progression Free Survival (PFS) and Secondary end points included Overall Survival (OS), Objective Response Rate (ORR) and Safety. In an updated analysis of the KEYNOTE-024 study, after a median follow up of 25.2 months, the median OS was 30 months in the KEYTRUDA® group and 14.2 months in the chemotherapy group (HR=0.63; P=0.002). This OS benefit was maintained even after adjusting for crossover.
The authors in this publication reported the 5-year efficacy and safety outcomes from this pivotal Phase III KEYNOTE-024 trial. The median time from randomization to data cutoff was 59.9 months. Among patients initially assigned to chemotherapy, 66% received subsequent anti PD-1 or PD-L1 therapy (66% cross over rate). In the KEYTRUDA® group, 52.9% received additional anticancer therapy.
The median OS was 26.3 months for KEYTRUDA® and 13.4 months for chemotherapy (HR=0.62). Kaplan-Meier estimates of the 5-year OS rate were 31.9% for the KEYTRUDA group and 16.3% for the chemotherapy group. The ORR was 46.1% among patients in the KEYTRUDA® group versus 31.1% in the chemotherapy group and the median Duration of Response was 29.1 months in the KEYTRUDA® group and 6.3 months in the chemotherapy group.
The authors concluded that first line KEYTRUDA® provides a durable and clinically meaningful long-term Overall Survival benefit, when compared to chemotherapy, in patients with metastatic NSCLC, with PD-L1 Tumor Proportion Score of at least 50%.They added that this is first 5-year follow up of any first line Phase III immunotherapy trial for Non Small Cell Lung Cancer.
Five-Year Efficacy Outcomes With Pembrolizumab vs Chemotherapy in Metastatic NSCLC With PD-L1 Tumor Proportion Score of at Least 50%: KEYNOTE-024 Trial. Reck M , Rodríguez–Abreu D, Robinson AG, et al. DOI: 10.1200/JCO.21.00174 Journal of Clinical Oncology. Published online April 19, 2021.