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FDA Approval of Pembrolizumab for HER2-Negative Gastric Cancer
The Food and Drug Administration approved pembrolizumab (Keytruda, Merck) in combination with fluoropyrimidine- and platinum-containing chemotherapy on November 16, 2023. This approval is for the initial treatment of adults with locally advanced unresectable or metastatic HER2-negative gastric or gastroesophageal junction (GEJ) adenocarcinoma.
KEYNOTE-859 Clinical Trial and Treatment Regimen
The effectiveness was assessed in a multicenter, randomized, double-blind, placebo-controlled experiment called KEYNOTE-859 (NCT03675737). The trial included 1579 patients with HER2-negative advanced gastric or GEJ adenocarcinoma who had not undergone systemic therapy for metastatic illness before. Participants were randomly assigned to receive either pembrolizumab 200 mg or a placebo along with the investigator’s choice of combination chemotherapy, which included either cisplatin 80 mg/m² plus 5-FU 800 mg/m²/day for 5 days (FP) or oxaliplatin 130 mg/m² on Day 1 plus capecitabine 1000 mg/m² twice a day for 14 days (CAPOX) in each 21-day cycle.
Clinical Efficacy and Survival Outcomes
The primary efficacy measure was overall survival (OS). The study also evaluated progression-free survival (PFS), overall response rate (ORR), and duration of response (DOR) through a blinded independent central review (BICR) based on RECIST v1.1 criteria, with a limit of 10 target lesions and 5 target lesions per organ.
Pembrolizumab combined with chemotherapy led to a statistically significant enhancement in overall survival (OS), progression-free survival (PFS), and objective response rate (ORR). The median overall survival was 12.9 months (95% CI: 11.9, 14.0) with pembrolizumab and 11.5 months (95% CI: 10.6, 12.1) with placebo. The hazard ratio (HR) was 0.78 (95% CI: 0.70, 0.87) with a p-value of <0.0001. The median progression-free survival (PFS) was 6.9 months (95% CI: 6.3, 7.2) and 5.6 months (95% CI: 5.5, 5.7) in the two groups, with a hazard ratio (HR) of 0.76 [95% CI: 0.67, 0.85] and a p-value of <0.0001. The objective response rate (ORR) was 51% (95% CI: 48, 55) and 42% (95% CI: 38, 45) with a statistically significant p-value of less than 0.0001 in the two treatment groups. The median duration of response (DOR) was 8 months (95% CI: 7.0, 9.7) for pembrolizumab and 5.7 months (95% CI: 5.5, 6.9) for placebo.
An additional study showed that patients who were given pembrolizumab and had tumors that expressed PD-L1 CPS > 1 and CPS ≥ 10 had statistically higher overall survival (OS), progression-free survival (PFS), and objective response rate (ORR).
Adverse Effects and Treatment Cessation
15% of patients experienced permanent cessation of pembrolizumab treatment due to adverse effects. Adverse effects leading to permanent cessation in at least 1% of cases included infections and diarrhea.
Recommended Dosage and Administration
The suggested dosage for pembrolizumab is 200 mg every 3 weeks or 400 mg every 6 weeks until disease progression or intolerable toxicity. Administer pembrolizumab before chemotherapy if they are given on the same day.
How CancerFax Helps
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About Susan Hau
Susan Hau is a distinguished researcher in the field of cancer cell therapy, with a particular focus on T cell-based approaches and cancer vaccines. Her work spans several innovative treatment modalities, including CAR T-cell therapy, TIL (Tumor-Infiltrating Lymphocyte) therapy, and NK (Natural Killer) cell therapy. Hau's expertise lies in cancer cell biolo…
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Medical Disclaimer
This article is for educational purposes only and should not replace medical advice, diagnosis, or treatment from a qualified oncology specialist. Every patient's case is different. Treatment decisions should always be made after a review of complete medical records by the treating medical team.
Treatment availability, eligibility, timelines, and access can change. Any clinical trial participation depends on detailed review and approval by the trial hospital or investigator.