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NCT03675737 · OUTCOME

Objective Response Rate (ORR) Per Response Evaluation Criteria in Solid Tumors Version 1.1 (RECIST 1.1) Assessed by Blinded Independent Central Review (BICR) in All Participants

Pembrolizumab (MK-3475) Plus Chemotherapy Versus Placebo Plus Chemotherapy in Participants Gastric or Gastroesophageal Junction (GEJ) Adenocarcinoma (MK-3475-859/KEYNOTE-859) · Source last updated 2026-02-27

Results reported by the registry submitting party. Population, time horizon, units and missing values must be read together.

Measure
NUMBER
Unit
Percentage of Participants
Interval / dispersion
95% Confidence Interval
Time frame
Up to 49.5 months

What was measured

ORR was defined as the percentage of the participants who had a confirmed Complete Response (CR: disappearance of all target lesions) or Partial Response (PR: ≥30% decrease in the sum of diameters (SOD) of target lesions, taking as reference the baseline SOD) according to RECIST 1.1 as assessed by BICR.

Analysis population: The analysis population included all randomized participants.

Groups in this outcome

Pembrolizumab + Chemotherapy (FP or CAPOX Regimen)

Participants received pembrolizumab 200 mg intravenously (IV) on Day 1 of each 21-day cycle (Q3W) for up to 35 cycles (approximately 2 years) + physicians' choice of either cisplatin 80 mg/m\^2 IV on Day 1 Q3W and 5-fluorouracil (5FU) 800 mg/m\^2/day via continuous IV infusion on Days 1 to 5 Q3W (FP regimen) OR oxaliplatin 130 mg/m\^2 IV on Day 1 Q3W + capecitabine 1000 mg/m\^2 orally twice a day (BID) on Days 1 to 14 Q3W (CAPOX regimen). Participants who completed up to 35 administrations of pembrolizumab (approximately 2 years) or achieved a complete response (CR) but experienced progression of disease (PD), could have initiated a second course of pembrolizumab for up to 17 cycles (approximately 1 additional year).

Placebo + Chemotherapy (FP or CAPOX Regimen)

Participants received placebo on Day 1 Q3W for up to 35 cycles (approximately 2 years) + physicians' choice of either cisplatin 80 mg/m\^2 IV on Day 1 Q3W and 5FU 800 mg/m\^2/day via continuous IV infusion on Days 1 to 5 Q3W (FP regimen) OR oxaliplatin 130 mg/m\^2 IV on Day 1 Q3W + capecitabine 1000 mg/m\^2 orally BID on Days 1 to 14 Q3W (CAPOX regimen).

Group identifiers and denominators belong to this outcome only. They may differ in another outcome or in safety reporting.

Analysis denominator · Participants

GroupSource count
Pembrolizumab + Chemotherapy (FP or CAPOX Regimen)790
Placebo + Chemotherapy (FP or CAPOX Regimen)789

Reported measurements

Source class 1
Values in Percentage of Participants · Interval/dispersion: 95% Confidence Interval
GroupValueSpreadLowerUpperComment
Pembrolizumab + Chemotherapy (FP or CAPOX Regimen)51.3Not reported47.754.8Not reported
Placebo + Chemotherapy (FP or CAPOX Regimen)42.0Not reported38.545.5Not reported

Source statistical analyses

Group order, estimate direction, methods and comments are retained. No treatment ranking is inferred.

  1. ci Lower Limit
    4.4
    ci Num Sides
    TWO_SIDED
    ci Pct Value
    95
    ci Upper Limit
    14.1
    estimate Comment
    Based on Miettinen \& Nurminen method stratified by geographic region, PD-L1 status (CPS \<1 versus CPS ≥1), and chemotherapy regimen with small strata collapsed.
    group Ids
    1. OG000
    2. OG001
    non Inferiority Type
    SUPERIORITY
    p Value
    0.00009
    p Value Comment
    One-sided p-value based on Miettinen \& Nurminen method stratified by geographic region, Programmed Cell Death Ligand 1 (PD-L1) status (Combined Positive Score \[CPS\] \<1 versus CPS ≥1), and chemotherapy regimen with small strata collapsed.
    param Type
    Difference in Percentage
    param Value
    9.3
    statistical Method
    Miettinen & Nurminen method
Complete source fields
analyses
  1. ci Lower Limit
    4.4
    ci Num Sides
    TWO_SIDED
    ci Pct Value
    95
    ci Upper Limit
    14.1
    estimate Comment
    Based on Miettinen \& Nurminen method stratified by geographic region, PD-L1 status (CPS \<1 versus CPS ≥1), and chemotherapy regimen with small strata collapsed.
    group Ids
    1. OG000
    2. OG001
    non Inferiority Type
    SUPERIORITY
    p Value
    0.00009
    p Value Comment
    One-sided p-value based on Miettinen \& Nurminen method stratified by geographic region, Programmed Cell Death Ligand 1 (PD-L1) status (Combined Positive Score \[CPS\] \<1 versus CPS ≥1), and chemotherapy regimen with small strata collapsed.
    param Type
    Difference in Percentage
    param Value
    9.3
    statistical Method
    Miettinen & Nurminen method
classes
  1. categories
    1. measurements
      1. group Id
        OG000
        lower Limit
        47.7
        upper Limit
        54.8
        value
        51.3
      2. group Id
        OG001
        lower Limit
        38.5
        upper Limit
        45.5
        value
        42.0
denoms
  1. counts
    1. group Id
      OG000
      value
      790
    2. group Id
      OG001
      value
      789
    units
    Participants
description
ORR was defined as the percentage of the participants who had a confirmed Complete Response (CR: disappearance of all target lesions) or Partial Response (PR: ≥30% decrease in the sum of diameters (SOD) of target lesions, taking as reference the baseline SOD) according to RECIST 1.1 as assessed by BICR.
dispersion Type
95% Confidence Interval
groups
  1. description
    Participants received pembrolizumab 200 mg intravenously (IV) on Day 1 of each 21-day cycle (Q3W) for up to 35 cycles (approximately 2 years) + physicians' choice of either cisplatin 80 mg/m\^2 IV on Day 1 Q3W and 5-fluorouracil (5FU) 800 mg/m\^2/day via continuous IV infusion on Days 1 to 5 Q3W (FP regimen) OR oxaliplatin 130 mg/m\^2 IV on Day 1 Q3W + capecitabine 1000 mg/m\^2 orally twice a day (BID) on Days 1 to 14 Q3W (CAPOX regimen). Participants who completed up to 35 administrations of pembrolizumab (approximately 2 years) or achieved a complete response (CR) but experienced progression of disease (PD), could have initiated a second course of pembrolizumab for up to 17 cycles (approximately 1 additional year).
    id
    OG000
    title
    Pembrolizumab + Chemotherapy (FP or CAPOX Regimen)
  2. description
    Participants received placebo on Day 1 Q3W for up to 35 cycles (approximately 2 years) + physicians' choice of either cisplatin 80 mg/m\^2 IV on Day 1 Q3W and 5FU 800 mg/m\^2/day via continuous IV infusion on Days 1 to 5 Q3W (FP regimen) OR oxaliplatin 130 mg/m\^2 IV on Day 1 Q3W + capecitabine 1000 mg/m\^2 orally BID on Days 1 to 14 Q3W (CAPOX regimen).
    id
    OG001
    title
    Placebo + Chemotherapy (FP or CAPOX Regimen)
param Type
NUMBER
population Description
The analysis population included all randomized participants.
reporting Status
POSTED
time Frame
Up to 49.5 months
title
Objective Response Rate (ORR) Per Response Evaluation Criteria in Solid Tumors Version 1.1 (RECIST 1.1) Assessed by Blinded Independent Central Review (BICR) in All Participants
type
SECONDARY
unit Of Measure
Percentage of Participants

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Preserved source evidence · Not medical advice