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NCT03675737 · OUTCOME

Progression Free Survival (PFS) 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
MEDIAN
Unit
Months
Interval / dispersion
95% Confidence Interval
Time frame
Up to 49.5 months

What was measured

PFS was defined as the time from randomization to the first documented progressive disease (PD) or death due to any cause, whichever occurred first. Per RECIST 1.1 as assessed by BICR, PD was defined as ≥20% increase in the sum of diameters of target lesions. In addition to the relative increase of 20%, the sum must also have demonstrated an absolute increase of ≥5 mm. The appearance of ≥1 new lesions was also considered PD. PFS was estimated using the product-limit (Kaplan-Meier) method for censored data.

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 Months · Interval/dispersion: 95% Confidence Interval
GroupValueSpreadLowerUpperComment
Pembrolizumab + Chemotherapy (FP or CAPOX Regimen)6.9Not reported6.37.2Not reported
Placebo + Chemotherapy (FP or CAPOX Regimen)5.6Not reported5.55.7Not reported

Source statistical analyses

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

  1. ci Lower Limit
    0.67
    ci Num Sides
    TWO_SIDED
    ci Pct Value
    95
    ci Upper Limit
    0.85
    estimate Comment
    Based on Cox regression model with Efron's method of tie handling with treatment as a covariate 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
    <0.0001
    p Value Comment
    One-sided p-value based on log-rank test 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
    Hazard Ratio (HR)
    param Value
    0.76
    statistical Method
    Log Rank
Complete source fields
analyses
  1. ci Lower Limit
    0.67
    ci Num Sides
    TWO_SIDED
    ci Pct Value
    95
    ci Upper Limit
    0.85
    estimate Comment
    Based on Cox regression model with Efron's method of tie handling with treatment as a covariate 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
    <0.0001
    p Value Comment
    One-sided p-value based on log-rank test 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
    Hazard Ratio (HR)
    param Value
    0.76
    statistical Method
    Log Rank
classes
  1. categories
    1. measurements
      1. group Id
        OG000
        lower Limit
        6.3
        upper Limit
        7.2
        value
        6.9
      2. group Id
        OG001
        lower Limit
        5.5
        upper Limit
        5.7
        value
        5.6
denoms
  1. counts
    1. group Id
      OG000
      value
      790
    2. group Id
      OG001
      value
      789
    units
    Participants
description
PFS was defined as the time from randomization to the first documented progressive disease (PD) or death due to any cause, whichever occurred first. Per RECIST 1.1 as assessed by BICR, PD was defined as ≥20% increase in the sum of diameters of target lesions. In addition to the relative increase of 20%, the sum must also have demonstrated an absolute increase of ≥5 mm. The appearance of ≥1 new lesions was also considered PD. PFS was estimated using the product-limit (Kaplan-Meier) method for censored data.
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
MEDIAN
population Description
The analysis population included all randomized participants.
reporting Status
POSTED
time Frame
Up to 49.5 months
title
Progression Free Survival (PFS) 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
Months

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Preserved source evidence · Not medical advice