Trial results for pembrolizumab (Keytruda) plus chemotherapy in participants with gastric or gastroesophageal junction adenocarcinoma were posted on ClinicalTrials.gov on 2025-02-20. The study found a pathological complete response (pathCR) rate of 6.8% for the pembrolizumab arm compared to 4.9% for the placebo arm.
Background
This study investigated pembrolizumab in combination with chemotherapy for the neoadjuvant or adjuvant treatment of previously untreated Chinese adults with gastric and gastroesophageal junction (GEJ) adenocarcinoma.
Trial design
The completed Phase 3 study (NCT04882241) enrolled 120 participants with gastric cancer or gastroesophageal junction cancer. Participants received either pembrolizumab plus chemotherapy (cisplatin, capecitabine, or 5-fluorouracil) or placebo plus the same chemotherapy regimen. The trial's brief summary stated that no formal hypothesis testing would be done.
Key results
Key outcome measurements and analyses from the trial include:
- Pathological Complete Response (pathCR) Rate: The pembrolizumab + XP/FP arm showed a pathCR rate of 6.8%, while the placebo + XP/FP arm showed a rate of 4.9%. The difference in percentage was 1.9% (95% Confidence Interval: -7.7% to 12.0%), with a p-value of 0.33244.
- Event-free Survival (EFS): The median EFS for the placebo + XP/FP arm was 36.5 months. The median EFS for the pembrolizumab + XP/FP arm was not available ("NA"). The Hazard Ratio (HR) for EFS was 0.92 (95% Confidence Interval: 0.5 to 1.7), with a p-value of 0.39528.
- Disease-free Survival (DFS): The median DFS for the placebo + XP/FP arm was 33.1 months. The median DFS for the pembrolizumab + XP/FP arm was not available ("NA"). The Hazard Ratio (HR) for DFS was 0.83 (95% Confidence Interval: 0.34 to 2.05), with a p-value of 0.34632.
- Overall Survival (OS): Median OS for both the pembrolizumab + XP/FP and placebo + XP/FP arms was not available ("NA"). The Hazard Ratio (HR) for OS was 1.03 (95% Confidence Interval: 0.48 to 2.22), with a p-value of 0.52903.
- Adverse Events (AEs): 59 participants in the pembrolizumab + XP/FP arm experienced one or more AEs, compared to 61 participants in the placebo + XP/FP arm. 12 participants in the pembrolizumab + XP/FP arm discontinued study treatment due to an AE, versus 8 participants in the placebo + XP/FP arm.
What this means
The trial results provide data on the use of pembrolizumab plus chemotherapy in gastric and gastroesophageal junction adenocarcinoma. While a numerical difference was observed in the pathological complete response rate, with 6.8% in the pembrolizumab arm versus 4.9% in the placebo arm, the statistical analysis indicated this difference was not significant (p-value 0.33244). Similarly, analyses for event-free survival, disease-free survival, and overall survival did not show statistically significant differences, and median values for the pembrolizumab arm were not available for these endpoints. The trial's design explicitly stated that no formal hypothesis testing would be done, which aligns with the non-significant p-values reported.
Source
The information regarding these trial results was obtained from ClinicalTrials.gov, a public database of clinical studies. The results for study NCT04882241, titled "Study of Pembrolizumab (MK-3475) Plus Chemotherapy Versus Placebo Plus Chemotherapy in Participants With Gastric or Gastroesophageal Junction (GEJ) Adenocarcinoma (MK-3475-585/KEYNOTE-585)-China Extension," were posted on 2025-02-20 on clinicaltrials.gov.