Efficacy Study of Nivolumab Plus Ipilimumab or Nivolumab Plus Chemotherapy Against Chemotherapy in Stomach Cancer or Stomach/Esophagus Junction Cancer

Inclusion Criteria

• Male or Female at least 18 years of age
• Must have gastric cancer or gastroesophageal junction cancer that cannot be operated on and that is advanced or has spread out
• Did not receive neoadjuvant or adjuvant treatment (chemotherapy, radiotherapy, or both) for their disease within the last 6 months
• Must have full activity or, if limited, must be able to walk and carry out light activities such as light house work or office work
• Must agree to provide tumor tissue sample, either from a previous surgery or biopsy within 6 months or fresh, prior to the start of treatment in this study

Exclusion Criteria

• Presence of tumor cells in the brain or spinal cord that have not been treated
• Active known or suspected autoimmune disease
• Any serious or uncontrolled medical disorder or active infection
• Known history of positive test for human immunodeficiency virus (HIV) or known acquired immunodeficiency syndrome (AIDS)
• Any positive test result for hepatitis B or C indicating acute or chronic infection Other protocol-defined inclusion/exclusion criteria apply