SUMMARY: Lung cancer is the second most common cancer in both men and women and accounts for about 13% of all new cancers and 21% of all cancer deaths. The American Cancer Society estimates that for 2023, about 238,340 new cases of lung cancer will be diagnosed and 127,070 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. With changes in the cigarette composition and decline in tobacco consumption over the past several decades, Adenocarcinoma now is the most frequent histologic subtype of lung cancer.
KEYTRUDA® 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, thereby undoing PD-1 pathway-mediated inhibition of the immune response and unleashing the tumor-specific effector T cells. High level of Programmed Death-Ligand 1 (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-189 is a double-blind, Phase III trial in which 616 patients with untreated Stage IV non-squamous NSCLC, without sensitizing EGFR or ALK mutations, were randomly assigned in a 2:1 ratio to receive treatment with four cycles of KEYTRUDA®/Pemetrexed/Carboplatin (N=410) or placebo plus the same chemotherapy (N=206). Patients then received either KEYTRUDA® 200 mg or saline placebo, both administered IV every 3 weeks for up to 35 cycles. All the patients received four cycles of the investigator’s choice of Cisplatin 75 mg/m2 IV or Carboplatin AUC 5 along with Pemetrexed 500 mg/m2, all administered IV every 3 weeks, followed by maintenance Pemetrexed 500 mg/m2 every 3 weeks. Patients in the placebo combination group were allowed to crossover to KEYTRUDA® monotherapy upon disease progression. Patients with symptomatic brain metastasis were excluded and patients were stratified according to PD-L1 expression (Tumor Proportion Score, 1% or more versus less than 1%), choice of platinum-based drug (Cisplatin versus Carboplatin), and smoking history. Both treatment groups were well balanced and about 17% had brain metastasis and one-third were untreated. A PD-L1 Tumor Proportion Score of 1% or more was reported in 63% of the patients, Carboplatin was the preferred platinum-based drug in 72% of the patients, and 88% of the patients were current or former smokers. The co-Primary end points were Overall Survival (OS) and Progression Free Survival (PFS). Secondary end points included Objective Response Rate (ORR) and Duration of Response (DOR) and Safety. Exploratory end points included PFS2 (time from random assignment to second/subsequent progressive disease on next-line treatment or death from any cause).
In the initial report from the trial, after a median follow-up of 10.5 months, the median PFS was 8.8 months in the KEYTRUDA® combination group and 4.9 months in the placebo combination group (HR=0.52; P<0.001) and the median OS was Not Reached with KEYTRUDA® combination and was 11.3 months in the placebo combination group (HR=0.49; P<0.001).
In this updated analysis, the researchers presented 5-year outcomes from the Phase III KEYNOTE-189 study. The median time from randomization to data cutoff (in March 2022) was 64.6 months. There was continued benefit in the Progression Free Survival and Overall Survival in the KEYTRUDA® group compared to the control group (HR=0.50 versus HR=0.60, respectively). The 5-year Progression Free Survival rates were 7.5% versus 0.6% and 5-year Overall Survival rates were 19.4% versus 11.3% respectively. The Objective Response Rate in the KEYTRUDA® group was 48.3% versus 19.9% in the control group, and the median Duration of Response was 12.7 and 7.1 months, respectively. Similar trends were observed across the PD-L1 subgroups analyzed. Among the 57 patients assigned to KEYTRUDA® combination and completed 35 cycles of KEYTRUDA®, the Objective Response Rate was 86% and the estimated Overall Survival rate 3 years after completion of 35 cycles (approximately 5 years from random assignment) was 71.9%. Sustained improvements in Overall Survival were observed in the KEYTRUDA® combination group, despite a crossover rate of 57% of patients from placebo plus chemotherapy to subsequent anti-PD1 therapy, further supporting the use of KEYTRUDA® plus chemotherapy as first-line treatment.
It was concluded that KEYTRUDA® in combination with Pemetrexed and Platinum chemotherapy continued to demonstrate prolonged survival and durable antitumor activity, compared to chemotherapy alone, regardless of PD-L1 expression. The authors added that these data continue to support the combination of first-line KEYTRUDA® plus a Platinum and Pemetrexed as a standard of care, in patients with previously untreated metastatic nonsquamous NSCLC, without EGFR/ALK alterations.
Pembrolizumab Plus Pemetrexed and Platinum in Nonsquamous Non–Small-Cell Lung Cancer: 5-Year Outcomes From the Phase 3 KEYNOTE-189 Study. Garassino MC, Gadgeel S, Speranza G, et al. DOI: 10.1200/JCO.22.01989 Journal of Clinical Oncology. Published online February 21, 2023.
