A Trial of Pembrolizumab With Chemotherapy or Chemoradiotherapy in Participants From India With Different Types of Cancer (MK-3475-G44/KEYNOTE-G44)

Inclusion Criteria: Cohort 1: * The participant must have a histologically or cytologically confirmed diagnosis of locally advanced unresectable or metastatic gastric or gastroesophageal junction (GEJ) adenocarcinoma, with locally confirmed programmed death-ligand 1 (PD-L1) CPS ≥1. * Has locally confirmed human epidermal growth factor receptor 2 (HER2) negative cancer. Cohort 2: \- Has a histologically confirmed diagnosis of advanced (metastatic) and/or unresectable (locally advanced) biliary tract cancer (BTC) (intra or extrahepatic cholangiocarcinoma or gallbladder cancer). Cohort 3: * Has high-risk locally advanced cervical cancer. * Has histologically confirmed squamous cell carcinoma, adenocarcinoma, or adenosquamous carcinoma of the cervix. All Cohorts: * If hepatitis B surface antigen (HBsAg)-positive, has undetectable hepatitis B virus (HBV) viral load and has received HBV antiviral therapy for at least 4 weeks and will continue it. * If history of hepatitis C virus (HCV) infection, has undetectable HCV viral load. Exclusion Criteria: Cohort 1: * Has squamous cell or undifferentiated gastric cancer. * Has had previous therapy for locally advanced, unresectable or metastatic gastric/GEJ cancer. * Has known active central nervous system (CNS) metastases and/or carcinomatous meningitis. * Has had major surgery, open biopsy, or significant traumatic injury within 28 days prior to first dose of study. * Had active hemoptysis (bright red blood of at least 0.5 teaspoon) within 3 weeks or tumor bleeding within 2 weeks prior to the first dose of study intervention. Cohort 2: * Has ampullary cancer. * Has small cell cancer, neuroendocrine tumors, lymphoma, sarcoma, mixed tumor histology, and/or mucinous cystic neoplasms. * Has had previous systemic therapy for advanced (metastatic) or unresectable (locally advanced) BTC (intra or extrahepatic cholangiocarcinoma or gallbladder cancer), with the exception of neoadjuvant/adjuvant therapy, which is allowed. * Has known active CNS metastases and/or carcinomatous meningitis. * Had active hemoptysis (bright red blood of at least 0.5 teaspoon) within 3 weeks or tumor bleeding within 2 weeks prior to the first dose of study intervention. Cohort 3: \- Has undergone a previous hysterectomy defined as removal of the entire uterus or will have a hysterectomy as part of their initial cervical cancer therapy. All Cohorts: * Has hypokalemia. * Has hypomagnesemia. * Has hypocalcemia. * Received prior therapy with an anti-programmed cell death protein 1 (PD-1), anti-PD-L1, or anti-programmed death-ligand 2 (PD-L2) agent, or with an agent directed to another stimulatory or coinhibitory T-cell receptor. * Has active autoimmune disease that has required systemic treatment in the past 2 years. * Has history of (noninfectious) pneumonitis/interstitial lung disease that required steroids or current pneumonitis/interstitial lung disease. * Has a known additional invasive malignancy that is progressing or has required active treatment within the past 3 years. * Has history of human immunodeficiency virus (HIV) infection. * Has known active tuberculosis. * Has not adequately recovered from major surgery or is having ongoing surgical complications.