Pembrolizumab (MK-3475) Plus Gemcitabine/Cisplatin Versus Placebo Plus Gemcitabine/Cisplatin for First-Line Advanced and/or Unresectable Biliary Tract Carcinoma (BTC) (MK-3475-966/KEYNOTE-966)

Progression-free Survival (PFS) Per Response Evaluation Criteria in Solid Tumors Version 1.1 (RECIST 1.1) as Assessed by Response Evaluation Criteria in Solid Tumors Version 1.1 (BICR)

PFS was defined as the time from randomization to the first documented progressive disease (PD) per RECIST 1.1 by BICR, or death due to any cause, whichever occurred first.

Time frame: Up to approximately 26 months

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

ORR was defined as the percentage of participants who have a confirmed Complete Response (CR: disappearance of all target lesions) or Partial Response (PR: a ≥30% decrease in the sum of diameters \[SOD\] of target lesions) as assessed by BICR per RECIST 1.1, which was adjusted for this study to allow a maximum of 10 target lesions in total and 5 per organ.

Time frame: Up to approximately 26 months

Duration of Response (DOR) Per RECIST 1.1 as Assessed by BICR

For participants who demonstrate a confirmed CR or PR, DOR was the time from the first documented evidence of CR or PR until disease progression or death due to any cause, whichever occurred first.

Time frame: Up to approximately 38 months

Number of Participants Who Experience One or More Adverse Events (AE)

An adverse event (AE) was defined as any unfavorable and unintended sign including an abnormal laboratory finding, symptom or disease associated with the use of a medical treatment or procedure, regardless of whether it was considered related to the medical treatment or procedure, that occurred during the course of the study.