Biobanking Upper Gastrointestinal Tumors to Evaluate Response (BURGER With BACON)

The goal of this observational study is to examine genetic changes that may contribute to immunotherapy resistance in gastroesophageal cancer. This information can potentially lead to the identification of new immunotherapeutic targets as well as improve the ability to identify those patients more likely to respond to immunotherapy. This study does not include any treatment or investigational drugs. Participants will be asked: * to enroll before beginning standard care of treatment for their cancer * for blood, archived tumor tissue, and fresh tumor tissue Researchers will compare participants who are not getting immunotherapy to identify potential differences in expression levels of a gene.