Siewert Type I Adenocarcinoma of Esophagogastric Junction

This interventional clinical trial aims to find ways of improving treatments for individuals with esophageal cancer. Laboratory-based studies show that using medicines that affect a protein called TGF-beta (TGFβ) can kill esophageal cancer cells in individuals who have localized esophageal adenocarcinoma and are being considered for standard-of-care chemoradiation prior to surgery. Participants of this study will take a pill called vactosertib for two weeks before starting standard of care therapy. At the end of the two weeks of taking vactosertib, participants will have a Positron Emission Tomography Computer Assisted Tomography (PET CT) scan and undergo an endoscopy with a biopsy to determine if the vactosertib is working. After standard of care therapy, participants will take vactosertib again for two weeks and then be considered for surgery.