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NCT03675737 · BASELINE

Baseline characteristics

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.

denoms
  1. counts
    1. group Id
      BG000
      value
      790
    2. group Id
      BG001
      value
      789
    3. group Id
      BG002
      value
      1579
    units
    Participants
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
    BG000
    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
    BG001
    title
    Placebo + Chemotherapy (FP or CAPOX Regimen)
  3. description
    Total of all reporting groups
    id
    BG002
    title
    Total
measures
  1. classes
    1. categories
      1. measurements
        1. group Id
          BG000
          spread
          11.9
          value
          59.3
        2. group Id
          BG001
          spread
          11.8
          value
          60.0
        3. group Id
          BG002
          spread
          11.8
          value
          59.6
    dispersion Type
    STANDARD_DEVIATION
    param Type
    MEAN
    title
    Age, Continuous
    unit Of Measure
    Years
  2. classes
    1. categories
      1. measurements
        1. group Id
          BG000
          value
          263
        2. group Id
          BG001
          value
          245
        3. group Id
          BG002
          value
          508
        title
        Female
      2. measurements
        1. group Id
          BG000
          value
          527
        2. group Id
          BG001
          value
          544
        3. group Id
          BG002
          value
          1071
        title
        Male
    param Type
    COUNT_OF_PARTICIPANTS
    title
    Sex: Female, Male
    unit Of Measure
    Participants
  3. classes
    1. categories
      1. measurements
        1. group Id
          BG000
          value
          175
        2. group Id
          BG001
          value
          157
        3. group Id
          BG002
          value
          332
        title
        Hispanic or Latino
      2. measurements
        1. group Id
          BG000
          value
          590
        2. group Id
          BG001
          value
          615
        3. group Id
          BG002
          value
          1205
        title
        Not Hispanic or Latino
      3. measurements
        1. group Id
          BG000
          value
          25
        2. group Id
          BG001
          value
          17
        3. group Id
          BG002
          value
          42
        title
        Unknown or Not Reported
    param Type
    COUNT_OF_PARTICIPANTS
    title
    Ethnicity (NIH/OMB)
    unit Of Measure
    Participants
  4. classes
    1. categories
      1. measurements
        1. group Id
          BG000
          value
          31
        2. group Id
          BG001
          value
          36
        3. group Id
          BG002
          value
          67
        title
        American Indian or Alaska Native
      2. measurements
        1. group Id
          BG000
          value
          270
        2. group Id
          BG001
          value
          269
        3. group Id
          BG002
          value
          539
        title
        Asian
      3. measurements
        1. group Id
          BG000
          value
          1
        2. group Id
          BG001
          value
          2
        3. group Id
          BG002
          value
          3
        title
        Native Hawaiian or Other Pacific Islander
      4. measurements
        1. group Id
          BG000
          value
          12
        2. group Id
          BG001
          value
          9
        3. group Id
          BG002
          value
          21
        title
        Black or African American
      5. measurements
        1. group Id
          BG000
          value
          426
        2. group Id
          BG001
          value
          435
        3. group Id
          BG002
          value
          861
        title
        White
      6. measurements
        1. group Id
          BG000
          value
          43
        2. group Id
          BG001
          value
          30
        3. group Id
          BG002
          value
          73
        title
        More than one race
      7. measurements
        1. group Id
          BG000
          value
          7
        2. group Id
          BG001
          value
          8
        3. group Id
          BG002
          value
          15
        title
        Unknown or Not Reported
    param Type
    COUNT_OF_PARTICIPANTS
    title
    Race (NIH/OMB)
    unit Of Measure
    Participants
  5. classes
    1. categories
      1. measurements
        1. group Id
          BG000
          value
          618
        2. group Id
          BG001
          value
          617
        3. group Id
          BG002
          value
          1235
      title
      CPS ≥1
    2. categories
      1. measurements
        1. group Id
          BG000
          value
          172
        2. group Id
          BG001
          value
          172
        3. group Id
          BG002
          value
          344
      title
      CPS <1
    description
    PD-L1 positivity at baseline was determined by immunohistochemistry (IHC) using both tumor and blood cells. Participants were stratified (CPS \<1 versus CPS ≥1) and some efficacy outcome measures were presented using a CPS cutoff of CPS ≥1 at baseline. Participants with a CPS \<1 were classified as PD-L1 negative, participants with a CPS≥1 were classified as PD-L1 positive.
    param Type
    COUNT_OF_PARTICIPANTS
    title
    Programmed Cell Death Ligand 1 (PD-L1) Combined Positive Score (CPS) <1 and CPS ≥1 Status
    unit Of Measure
    Participants
  6. classes
    1. categories
      1. measurements
        1. group Id
          BG000
          value
          280
        2. group Id
          BG001
          value
          273
        3. group Id
          BG002
          value
          553
      title
      CPS ≥10
    2. categories
      1. measurements
        1. group Id
          BG000
          value
          508
        2. group Id
          BG001
          value
          516
        3. group Id
          BG002
          value
          1024
      title
      CPS <10
    3. categories
      1. measurements
        1. group Id
          BG000
          value
          2
        2. group Id
          BG001
          value
          0
        3. group Id
          BG002
          value
          2
      title
      Unknown
    description
    PD-L1 positivity at baseline was determined by immunohistochemistry (IHC) using both tumor and blood cells. Some efficacy outcome measures were presented using a CPS cutoff of CPS ≥10 at baseline. Participants with a CPS ≥10 were classified as PD-L1 strongly positive.
    param Type
    COUNT_OF_PARTICIPANTS
    title
    Programmed Cell Death Ligand 1 (PD-L1) Combined Positive Score (CPS) ≥10 Status
    unit Of Measure
    Participants
  7. classes
    1. categories
      1. measurements
        1. group Id
          BG000
          value
          108
        2. group Id
          BG001
          value
          108
        3. group Id
          BG002
          value
          216
      title
      FP Regimen
    2. categories
      1. measurements
        1. group Id
          BG000
          value
          682
        2. group Id
          BG001
          value
          681
        3. group Id
          BG002
          value
          1363
      title
      CAPOX Regimen
    description
    Participants received the physicians' choice of either the FP chemotherapy regimen (cisplatin and 5FU) OR the CAPOX regimen (oxaliplatin and capecitabine). Participants were stratified by chemotherapy regimen.
    param Type
    COUNT_OF_PARTICIPANTS
    title
    Chemotherapy Regimen
    unit Of Measure
    Participants
  8. classes
    1. categories
      1. measurements
        1. group Id
          BG000
          value
          201
        2. group Id
          BG001
          value
          202
        3. group Id
          BG002
          value
          403
      title
      Western Europe/Israel/North America/Australia
    2. categories
      1. measurements
        1. group Id
          BG000
          value
          263
        2. group Id
          BG001
          value
          262
        3. group Id
          BG002
          value
          525
      title
      Asia
    3. categories
      1. measurements
        1. group Id
          BG000
          value
          326
        2. group Id
          BG001
          value
          325
        3. group Id
          BG002
          value
          651
      title
      Rest of World
    description
    Participants were stratified by geographic region using the following categories: Western Europe/Israel/North America/Australia; Asia; and Rest of World.
    param Type
    COUNT_OF_PARTICIPANTS
    title
    Geographic Region
    unit Of Measure
    Participants
population Description
All randomized participants
Complete source fields
denoms
  1. counts
    1. group Id
      BG000
      value
      790
    2. group Id
      BG001
      value
      789
    3. group Id
      BG002
      value
      1579
    units
    Participants
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
    BG000
    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
    BG001
    title
    Placebo + Chemotherapy (FP or CAPOX Regimen)
  3. description
    Total of all reporting groups
    id
    BG002
    title
    Total
measures
  1. classes
    1. categories
      1. measurements
        1. group Id
          BG000
          spread
          11.9
          value
          59.3
        2. group Id
          BG001
          spread
          11.8
          value
          60.0
        3. group Id
          BG002
          spread
          11.8
          value
          59.6
    dispersion Type
    STANDARD_DEVIATION
    param Type
    MEAN
    title
    Age, Continuous
    unit Of Measure
    Years
  2. classes
    1. categories
      1. measurements
        1. group Id
          BG000
          value
          263
        2. group Id
          BG001
          value
          245
        3. group Id
          BG002
          value
          508
        title
        Female
      2. measurements
        1. group Id
          BG000
          value
          527
        2. group Id
          BG001
          value
          544
        3. group Id
          BG002
          value
          1071
        title
        Male
    param Type
    COUNT_OF_PARTICIPANTS
    title
    Sex: Female, Male
    unit Of Measure
    Participants
  3. classes
    1. categories
      1. measurements
        1. group Id
          BG000
          value
          175
        2. group Id
          BG001
          value
          157
        3. group Id
          BG002
          value
          332
        title
        Hispanic or Latino
      2. measurements
        1. group Id
          BG000
          value
          590
        2. group Id
          BG001
          value
          615
        3. group Id
          BG002
          value
          1205
        title
        Not Hispanic or Latino
      3. measurements
        1. group Id
          BG000
          value
          25
        2. group Id
          BG001
          value
          17
        3. group Id
          BG002
          value
          42
        title
        Unknown or Not Reported
    param Type
    COUNT_OF_PARTICIPANTS
    title
    Ethnicity (NIH/OMB)
    unit Of Measure
    Participants
  4. classes
    1. categories
      1. measurements
        1. group Id
          BG000
          value
          31
        2. group Id
          BG001
          value
          36
        3. group Id
          BG002
          value
          67
        title
        American Indian or Alaska Native
      2. measurements
        1. group Id
          BG000
          value
          270
        2. group Id
          BG001
          value
          269
        3. group Id
          BG002
          value
          539
        title
        Asian
      3. measurements
        1. group Id
          BG000
          value
          1
        2. group Id
          BG001
          value
          2
        3. group Id
          BG002
          value
          3
        title
        Native Hawaiian or Other Pacific Islander
      4. measurements
        1. group Id
          BG000
          value
          12
        2. group Id
          BG001
          value
          9
        3. group Id
          BG002
          value
          21
        title
        Black or African American
      5. measurements
        1. group Id
          BG000
          value
          426
        2. group Id
          BG001
          value
          435
        3. group Id
          BG002
          value
          861
        title
        White
      6. measurements
        1. group Id
          BG000
          value
          43
        2. group Id
          BG001
          value
          30
        3. group Id
          BG002
          value
          73
        title
        More than one race
      7. measurements
        1. group Id
          BG000
          value
          7
        2. group Id
          BG001
          value
          8
        3. group Id
          BG002
          value
          15
        title
        Unknown or Not Reported
    param Type
    COUNT_OF_PARTICIPANTS
    title
    Race (NIH/OMB)
    unit Of Measure
    Participants
  5. classes
    1. categories
      1. measurements
        1. group Id
          BG000
          value
          618
        2. group Id
          BG001
          value
          617
        3. group Id
          BG002
          value
          1235
      title
      CPS ≥1
    2. categories
      1. measurements
        1. group Id
          BG000
          value
          172
        2. group Id
          BG001
          value
          172
        3. group Id
          BG002
          value
          344
      title
      CPS <1
    description
    PD-L1 positivity at baseline was determined by immunohistochemistry (IHC) using both tumor and blood cells. Participants were stratified (CPS \<1 versus CPS ≥1) and some efficacy outcome measures were presented using a CPS cutoff of CPS ≥1 at baseline. Participants with a CPS \<1 were classified as PD-L1 negative, participants with a CPS≥1 were classified as PD-L1 positive.
    param Type
    COUNT_OF_PARTICIPANTS
    title
    Programmed Cell Death Ligand 1 (PD-L1) Combined Positive Score (CPS) <1 and CPS ≥1 Status
    unit Of Measure
    Participants
  6. classes
    1. categories
      1. measurements
        1. group Id
          BG000
          value
          280
        2. group Id
          BG001
          value
          273
        3. group Id
          BG002
          value
          553
      title
      CPS ≥10
    2. categories
      1. measurements
        1. group Id
          BG000
          value
          508
        2. group Id
          BG001
          value
          516
        3. group Id
          BG002
          value
          1024
      title
      CPS <10
    3. categories
      1. measurements
        1. group Id
          BG000
          value
          2
        2. group Id
          BG001
          value
          0
        3. group Id
          BG002
          value
          2
      title
      Unknown
    description
    PD-L1 positivity at baseline was determined by immunohistochemistry (IHC) using both tumor and blood cells. Some efficacy outcome measures were presented using a CPS cutoff of CPS ≥10 at baseline. Participants with a CPS ≥10 were classified as PD-L1 strongly positive.
    param Type
    COUNT_OF_PARTICIPANTS
    title
    Programmed Cell Death Ligand 1 (PD-L1) Combined Positive Score (CPS) ≥10 Status
    unit Of Measure
    Participants
  7. classes
    1. categories
      1. measurements
        1. group Id
          BG000
          value
          108
        2. group Id
          BG001
          value
          108
        3. group Id
          BG002
          value
          216
      title
      FP Regimen
    2. categories
      1. measurements
        1. group Id
          BG000
          value
          682
        2. group Id
          BG001
          value
          681
        3. group Id
          BG002
          value
          1363
      title
      CAPOX Regimen
    description
    Participants received the physicians' choice of either the FP chemotherapy regimen (cisplatin and 5FU) OR the CAPOX regimen (oxaliplatin and capecitabine). Participants were stratified by chemotherapy regimen.
    param Type
    COUNT_OF_PARTICIPANTS
    title
    Chemotherapy Regimen
    unit Of Measure
    Participants
  8. classes
    1. categories
      1. measurements
        1. group Id
          BG000
          value
          201
        2. group Id
          BG001
          value
          202
        3. group Id
          BG002
          value
          403
      title
      Western Europe/Israel/North America/Australia
    2. categories
      1. measurements
        1. group Id
          BG000
          value
          263
        2. group Id
          BG001
          value
          262
        3. group Id
          BG002
          value
          525
      title
      Asia
    3. categories
      1. measurements
        1. group Id
          BG000
          value
          326
        2. group Id
          BG001
          value
          325
        3. group Id
          BG002
          value
          651
      title
      Rest of World
    description
    Participants were stratified by geographic region using the following categories: Western Europe/Israel/North America/Australia; Asia; and Rest of World.
    param Type
    COUNT_OF_PARTICIPANTS
    title
    Geographic Region
    unit Of Measure
    Participants
population Description
All randomized participants

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Preserved source evidence · Not medical advice