Study of Pembrolizumab (MK-3475) Versus Chemotherapy in Chinese Participants With Stage IV Colorectal Cancer (MK-3475-C66)

The main inclusion and exclusion criteria include but are not limited to the following: Inclusion Criteria: Inclusion Criteria include, but are not limited to: * Has a histologically confirmed diagnosis of colorectal adenocarcinoma that is at stage IV (as defined by American Joint Committee on Cancer eighth edition) \[National Comprehensive Cancer Network 2018\] * Has centrally confirmed Microsatellite Instability-High/Mismatch Repair Deficient (MSI-H/dMMR) status * Has centrally confirmed RAS and BRAF mutation status * A woman of child-bearing potential (WOCBP) must have a negative highly sensitive pregnancy test (urine or serum as required by local regulations) within 24 hours for urine or within 72 hours for serum before the first dose of study intervention. * Has measurable disease per Response Evaluation Criteria In Solid Tumors (RECIST) 1.1 as assessed by the local site investigator/radiology * Must provide an archival tumor tissue sample or newly obtained core or excisional biopsy of a tumor lesion not previously irradiated. * Has an Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 1 within 3 days before randomization * Has a life expectancy of at least 3 months * Has received Hepatitis B Virus (HBV) antiviral therapy for at least 4 weeks, and have undetectable hepatitis B virus (HBV) viral load prior to randomization if hepatitis B surface antigen (HBsAg) positive * Has an undetectable Hepatitis C Virus (HCV) viral load if HCV infected * Has wel…