Participants received pembrolizumab 200 mg intravenously (IV) on Day 1 of each 3-week cycle (Q3W) for 5 cycles followed by pembrolizumab 400 mg IV on Day 1 of each 6-week cycle (Q6W) for an additional 15 cycles. During the Q3W dosing period of pembrolizumab, participants received concurrent chemoradiotherapy. The standard of care chemoradiotherapy regimen includes cisplatin 40 mg/m^2 IV once per week (QW) for 5 or 6 weeks plus external beam radiotherapy (EBRT) followed by brachytherapy with minimum total radiotherapy dose of 80 Gray Units (Gy) for volume-directed and 75 Gy for point-directed given with the total duration of radiation treatment not to exceed 50 days (with an extension to a maximum of 56 days for unforeseen delays).

Participants received placebo for pembrolizumab IV on Day 1 of each 3-week cycle (Q3W) for 5 cycles followed by placebo IV on Day 1 of each 6-week cycle (Q6W) for an additional 15 cycles. During the Q3W dosing period of placebo, participants received concurrent chemoradiotherapy. The standard of care chemoradiotherapy regimen includes cisplatin 40 mg/m^2 IV once per week (QW) for 5 or 6 weeks plus external beam radiotherapy (EBRT) followed by brachytherapy with minimum total radiotherapy dose of 80 Gray Units (Gy) for volume-directed and 75 Gy for point-directed given with the total duration of radiation treatment not to exceed 50 days (with an extension to a maximum of 56 days for unforeseen delays).

Stratified by planned type of external beam radiation therapy (EBRT), stage at screening, and planned total radiotherapy dose.

One sided p-value

Based on Cox regression model with Efron's method of tie handling with treatment as a covariate

Participants received pembrolizumab 200 mg intravenously (IV) on Day 1 of each 3-week cycle (Q3W) for 5 cycles followed by pembrolizumab 400 mg IV on Day 1 of each 6-week cycle (Q6W) for an additional 15 cycles. During the Q3W dosing period of pembrolizumab, participants received concurrent chemoradiotherapy. The standard of care chemoradiotherapy regimen includes cisplatin 40 mg/m^2 IV once per week (QW) for 5 or 6 weeks plus external beam radiotherapy (EBRT) followed by brachytherapy with minimum total radiotherapy dose of 80 Gray Units (Gy) for volume-directed and 75 Gy for point-directed given with the total duration of radiation treatment not to exceed 50 days (with an extension to a maximum of 56 days for unforeseen delays).

Participants received placebo for pembrolizumab IV on Day 1 of each 3-week cycle (Q3W) for 5 cycles followed by placebo IV on Day 1 of each 6-week cycle (Q6W) for an additional 15 cycles. During the Q3W dosing period of placebo, participants received concurrent chemoradiotherapy. The standard of care chemoradiotherapy regimen includes cisplatin 40 mg/m^2 IV once per week (QW) for 5 or 6 weeks plus external beam radiotherapy (EBRT) followed by brachytherapy with minimum total radiotherapy dose of 80 Gray Units (Gy) for volume-directed and 75 Gy for point-directed given with the total duration of radiation treatment not to exceed 50 days (with an extension to a maximum of 56 days for unforeseen delays).

Participants received pembrolizumab 200 mg intravenously (IV) on Day 1 of each 3-week cycle (Q3W) for 5 cycles followed by pembrolizumab 400 mg IV on Day 1 of each 6-week cycle (Q6W) for an additional 15 cycles. During the Q3W dosing period of pembrolizumab, participants received concurrent chemoradiotherapy. The standard of care chemoradiotherapy regimen includes cisplatin 40 mg/m^2 IV once per week (QW) for 5 or 6 weeks plus external beam radiotherapy (EBRT) followed by brachytherapy with minimum total radiotherapy dose of 80 Gray Units (Gy) for volume-directed and 75 Gy for point-directed given with the total duration of radiation treatment not to exceed 50 days (with an extension to a maximum of 56 days for unforeseen delays).

Participants received pembrolizumab 200 mg intravenously (IV) on Day 1 of each 3-week cycle (Q3W) for 5 cycles followed by pembrolizumab 400 mg IV on Day 1 of each 6-week cycle (Q6W) for an additional 15 cycles. During the Q3W dosing period of pembrolizumab, participants received concurrent chemoradiotherapy. The standard of care chemoradiotherapy regimen includes cisplatin 40 mg/m^2 IV once per week (QW) for 5 or 6 weeks plus external beam radiotherapy (EBRT) followed by brachytherapy with minimum total radiotherapy dose of 80 Gray Units (Gy) for volume-directed and 75 Gy for point-directed given with the total duration of radiation treatment not to exceed 50 days (with an extension to a maximum of 56 days for unforeseen delays).

Participants received pembrolizumab 200 mg intravenously (IV) on Day 1 of each 3-week cycle (Q3W) for 5 cycles followed by pembrolizumab 400 mg IV on Day 1 of each 6-week cycle (Q6W) for an additional 15 cycles. During the Q3W dosing period of pembrolizumab, participants received concurrent chemoradiotherapy. The standard of care chemoradiotherapy regimen includes cisplatin 40 mg/m^2 IV once per week (QW) for 5 or 6 weeks plus external beam radiotherapy (EBRT) followed by brachytherapy with minimum total radiotherapy dose of 80 Gray Units (Gy) for volume-directed and 75 Gy for point-directed given with the total duration of radiation treatment not to exceed 50 days (with an extension to a maximum of 56 days for unforeseen delays).

Participants received pembrolizumab 200 mg intravenously (IV) on Day 1 of each 3-week cycle (Q3W) for 5 cycles followed by pembrolizumab 400 mg IV on Day 1 of each 6-week cycle (Q6W) for an additional 15 cycles. During the Q3W dosing period of pembrolizumab, participants received concurrent chemoradiotherapy. The standard of care chemoradiotherapy regimen includes cisplatin 40 mg/m^2 IV once per week (QW) for 5 or 6 weeks plus external beam radiotherapy (EBRT) followed by brachytherapy with minimum total radiotherapy dose of 80 Gray Units (Gy) for volume-directed and 75 Gy for point-directed given with the total duration of radiation treatment not to exceed 50 days (with an extension to a maximum of 56 days for unforeseen delays).

Participants received placebo for pembrolizumab IV on Day 1 of each 3-week cycle (Q3W) for 5 cycles followed by placebo IV on Day 1 of each 6-week cycle (Q6W) for an additional 15 cycles. During the Q3W dosing period of placebo, participants received concurrent chemoradiotherapy. The standard of care chemoradiotherapy regimen includes cisplatin 40 mg/m^2 IV once per week (QW) for 5 or 6 weeks plus external beam radiotherapy (EBRT) followed by brachytherapy with minimum total radiotherapy dose of 80 Gray Units (Gy) for volume-directed and 75 Gy for point-directed given with the total duration of radiation treatment not to exceed 50 days (with an extension to a maximum of 56 days for unforeseen delays).

Participants received pembrolizumab 200 mg intravenously (IV) on Day 1 of each 3-week cycle (Q3W) for 5 cycles followed by pembrolizumab 400 mg IV on Day 1 of each 6-week cycle (Q6W) for an additional 15 cycles. During the Q3W dosing period of pembrolizumab, participants received concurrent chemoradiotherapy. The standard of care chemoradiotherapy regimen includes cisplatin 40 mg/m^2 IV once per week (QW) for 5 or 6 weeks plus external beam radiotherapy (EBRT) followed by brachytherapy with minimum total radiotherapy dose of 80 Gray Units (Gy) for volume-directed and 75 Gy for point-directed given with the total duration of radiation treatment not to exceed 50 days (with an extension to a maximum of 56 days for unforeseen delays).

Participants received pembrolizumab 200 mg intravenously (IV) on Day 1 of each 3-week cycle (Q3W) for 5 cycles followed by pembrolizumab 400 mg IV on Day 1 of each 6-week cycle (Q6W) for an additional 15 cycles. During the Q3W dosing period of pembrolizumab, participants received concurrent chemoradiotherapy. The standard of care chemoradiotherapy regimen includes cisplatin 40 mg/m^2 IV once per week (QW) for 5 or 6 weeks plus external beam radiotherapy (EBRT) followed by brachytherapy with minimum total radiotherapy dose of 80 Gray Units (Gy) for volume-directed and 75 Gy for point-directed given with the total duration of radiation treatment not to exceed 50 days (with an extension to a maximum of 56 days for unforeseen delays).

Participants received pembrolizumab 200 mg intravenously (IV) on Day 1 of each 3-week cycle (Q3W) for 5 cycles followed by pembrolizumab 400 mg IV on Day 1 of each 6-week cycle (Q6W) for an additional 15 cycles. During the Q3W dosing period of pembrolizumab, participants received concurrent chemoradiotherapy. The standard of care chemoradiotherapy regimen includes cisplatin 40 mg/m^2 IV once per week (QW) for 5 or 6 weeks plus external beam radiotherapy (EBRT) followed by brachytherapy with minimum total radiotherapy dose of 80 Gray Units (Gy) for volume-directed and 75 Gy for point-directed given with the total duration of radiation treatment not to exceed 50 days (with an extension to a maximum of 56 days for unforeseen delays).

Participants received pembrolizumab 200 mg intravenously (IV) on Day 1 of each 3-week cycle (Q3W) for 5 cycles followed by pembrolizumab 400 mg IV on Day 1 of each 6-week cycle (Q6W) for an additional 15 cycles. During the Q3W dosing period of pembrolizumab, participants received concurrent chemoradiotherapy. The standard of care chemoradiotherapy regimen includes cisplatin 40 mg/m^2 IV once per week (QW) for 5 or 6 weeks plus external beam radiotherapy (EBRT) followed by brachytherapy with minimum total radiotherapy dose of 80 Gray Units (Gy) for volume-directed and 75 Gy for point-directed given with the total duration of radiation treatment not to exceed 50 days (with an extension to a maximum of 56 days for unforeseen delays).

Participants received pembrolizumab 200 mg intravenously (IV) on Day 1 of each 3-week cycle (Q3W) for 5 cycles followed by pembrolizumab 400 mg IV on Day 1 of each 6-week cycle (Q6W) for an additional 15 cycles. During the Q3W dosing period of pembrolizumab, participants received concurrent chemoradiotherapy. The standard of care chemoradiotherapy regimen includes cisplatin 40 mg/m^2 IV once per week (QW) for 5 or 6 weeks plus external beam radiotherapy (EBRT) followed by brachytherapy with minimum total radiotherapy dose of 80 Gray Units (Gy) for volume-directed and 75 Gy for point-directed given with the total duration of radiation treatment not to exceed 50 days (with an extension to a maximum of 56 days for unforeseen delays).

Participants received pembrolizumab 200 mg intravenously (IV) on Day 1 of each 3-week cycle (Q3W) for 5 cycles followed by pembrolizumab 400 mg IV on Day 1 of each 6-week cycle (Q6W) for an additional 15 cycles. During the Q3W dosing period of pembrolizumab, participants received concurrent chemoradiotherapy. The standard of care chemoradiotherapy regimen includes cisplatin 40 mg/m^2 IV once per week (QW) for 5 or 6 weeks plus external beam radiotherapy (EBRT) followed by brachytherapy with minimum total radiotherapy dose of 80 Gray Units (Gy) for volume-directed and 75 Gy for point-directed given with the total duration of radiation treatment not to exceed 50 days (with an extension to a maximum of 56 days for unforeseen delays).

Participants received pembrolizumab 200 mg intravenously (IV) on Day 1 of each 3-week cycle (Q3W) for 5 cycles followed by pembrolizumab 400 mg IV on Day 1 of each 6-week cycle (Q6W) for an additional 15 cycles. During the Q3W dosing period of pembrolizumab, participants received concurrent chemoradiotherapy. The standard of care chemoradiotherapy regimen includes cisplatin 40 mg/m^2 IV once per week (QW) for 5 or 6 weeks plus external beam radiotherapy (EBRT) followed by brachytherapy with minimum total radiotherapy dose of 80 Gray Units (Gy) for volume-directed and 75 Gy for point-directed given with the total duration of radiation treatment not to exceed 50 days (with an extension to a maximum of 56 days for unforeseen delays).

Participants received placebo for pembrolizumab IV on Day 1 of each 3-week cycle (Q3W) for 5 cycles followed by placebo IV on Day 1 of each 6-week cycle (Q6W) for an additional 15 cycles. During the Q3W dosing period of placebo, participants received concurrent chemoradiotherapy. The standard of care chemoradiotherapy regimen includes cisplatin 40 mg/m^2 IV once per week (QW) for 5 or 6 weeks plus external beam radiotherapy (EBRT) followed by brachytherapy with minimum total radiotherapy dose of 80 Gray Units (Gy) for volume-directed and 75 Gy for point-directed given with the total duration of radiation treatment not to exceed 50 days (with an extension to a maximum of 56 days for unforeseen delays).

Participants received pembrolizumab 200 mg intravenously (IV) on Day 1 of each 3-week cycle (Q3W) for 5 cycles followed by pembrolizumab 400 mg IV on Day 1 of each 6-week cycle (Q6W) for an additional 15 cycles. During the Q3W dosing period of pembrolizumab, participants received concurrent chemoradiotherapy. The standard of care chemoradiotherapy regimen includes cisplatin 40 mg/m^2 IV once per week (QW) for 5 or 6 weeks plus external beam radiotherapy (EBRT) followed by brachytherapy with minimum total radiotherapy dose of 80 Gray Units (Gy) for volume-directed and 75 Gy for point-directed given with the total duration of radiation treatment not to exceed 50 days (with an extension to a maximum of 56 days for unforeseen delays).

Participants received placebo for pembrolizumab IV on Day 1 of each 3-week cycle (Q3W) for 5 cycles followed by placebo IV on Day 1 of each 6-week cycle (Q6W) for an additional 15 cycles. During the Q3W dosing period of placebo, participants received concurrent chemoradiotherapy. The standard of care chemoradiotherapy regimen includes cisplatin 40 mg/m^2 IV once per week (QW) for 5 or 6 weeks plus external beam radiotherapy (EBRT) followed by brachytherapy with minimum total radiotherapy dose of 80 Gray Units (Gy) for volume-directed and 75 Gy for point-directed given with the total duration of radiation treatment not to exceed 50 days (with an extension to a maximum of 56 days for unforeseen delays).

Participants received pembrolizumab 200 mg intravenously (IV) on Day 1 of each 3-week cycle (Q3W) for 5 cycles followed by pembrolizumab 400 mg IV on Day 1 of each 6-week cycle (Q6W) for an additional 15 cycles. During the Q3W dosing period of pembrolizumab, participants received concurrent chemoradiotherapy. The standard of care chemoradiotherapy regimen includes cisplatin 40 mg/m^2 IV once per week (QW) for 5 or 6 weeks plus external beam radiotherapy (EBRT) followed by brachytherapy with minimum total radiotherapy dose of 80 Gray Units (Gy) for volume-directed and 75 Gy for point-directed given with the total duration of radiation treatment not to exceed 50 days (with an extension to a maximum of 56 days for unforeseen delays).

Participants received pembrolizumab 200 mg intravenously (IV) on Day 1 of each 3-week cycle (Q3W) for 5 cycles followed by pembrolizumab 400 mg IV on Day 1 of each 6-week cycle (Q6W) for an additional 15 cycles. During the Q3W dosing period of pembrolizumab, participants received concurrent chemoradiotherapy. The standard of care chemoradiotherapy regimen includes cisplatin 40 mg/m^2 IV once per week (QW) for 5 or 6 weeks plus external beam radiotherapy (EBRT) followed by brachytherapy with minimum total radiotherapy dose of 80 Gray Units (Gy) for volume-directed and 75 Gy for point-directed given with the total duration of radiation treatment not to exceed 50 days (with an extension to a maximum of 56 days for unforeseen delays).

Participants received pembrolizumab 200 mg intravenously (IV) on Day 1 of each 3-week cycle (Q3W) for 5 cycles followed by pembrolizumab 400 mg IV on Day 1 of each 6-week cycle (Q6W) for an additional 15 cycles. During the Q3W dosing period of pembrolizumab, participants received concurrent chemoradiotherapy. The standard of care chemoradiotherapy regimen includes cisplatin 40 mg/m^2 IV once per week (QW) for 5 or 6 weeks plus external beam radiotherapy (EBRT) followed by brachytherapy with minimum total radiotherapy dose of 80 Gray Units (Gy) for volume-directed and 75 Gy for point-directed given with the total duration of radiation treatment not to exceed 50 days (with an extension to a maximum of 56 days for unforeseen delays).

Participants received pembrolizumab 200 mg intravenously (IV) on Day 1 of each 3-week cycle (Q3W) for 5 cycles followed by pembrolizumab 400 mg IV on Day 1 of each 6-week cycle (Q6W) for an additional 15 cycles. During the Q3W dosing period of pembrolizumab, participants received concurrent chemoradiotherapy. The standard of care chemoradiotherapy regimen includes cisplatin 40 mg/m^2 IV once per week (QW) for 5 or 6 weeks plus external beam radiotherapy (EBRT) followed by brachytherapy with minimum total radiotherapy dose of 80 Gray Units (Gy) for volume-directed and 75 Gy for point-directed given with the total duration of radiation treatment not to exceed 50 days (with an extension to a maximum of 56 days for unforeseen delays).

Participants received placebo for pembrolizumab IV on Day 1 of each 3-week cycle (Q3W) for 5 cycles followed by placebo IV on Day 1 of each 6-week cycle (Q6W) for an additional 15 cycles. During the Q3W dosing period of placebo, participants received concurrent chemoradiotherapy. The standard of care chemoradiotherapy regimen includes cisplatin 40 mg/m^2 IV once per week (QW) for 5 or 6 weeks plus external beam radiotherapy (EBRT) followed by brachytherapy with minimum total radiotherapy dose of 80 Gray Units (Gy) for volume-directed and 75 Gy for point-directed given with the total duration of radiation treatment not to exceed 50 days (with an extension to a maximum of 56 days for unforeseen delays).

Participants received pembrolizumab 200 mg intravenously (IV) on Day 1 of each 3-week cycle (Q3W) for 5 cycles followed by pembrolizumab 400 mg IV on Day 1 of each 6-week cycle (Q6W) for an additional 15 cycles. During the Q3W dosing period of pembrolizumab, participants received concurrent chemoradiotherapy. The standard of care chemoradiotherapy regimen includes cisplatin 40 mg/m^2 IV once per week (QW) for 5 or 6 weeks plus external beam radiotherapy (EBRT) followed by brachytherapy with minimum total radiotherapy dose of 80 Gray Units (Gy) for volume-directed and 75 Gy for point-directed given with the total duration of radiation treatment not to exceed 50 days (with an extension to a maximum of 56 days for unforeseen delays).

Participants received placebo for pembrolizumab IV on Day 1 of each 3-week cycle (Q3W) for 5 cycles followed by placebo IV on Day 1 of each 6-week cycle (Q6W) for an additional 15 cycles. During the Q3W dosing period of placebo, participants received concurrent chemoradiotherapy. The standard of care chemoradiotherapy regimen includes cisplatin 40 mg/m^2 IV once per week (QW) for 5 or 6 weeks plus external beam radiotherapy (EBRT) followed by brachytherapy with minimum total radiotherapy dose of 80 Gray Units (Gy) for volume-directed and 75 Gy for point-directed given with the total duration of radiation treatment not to exceed 50 days (with an extension to a maximum of 56 days for unforeseen delays).