Perioperative FLOT(D) With Personalized Ultrafractionated Stereotactic Adaptive Radiotherapy (PULSAR) in Esophageal Cancer

The goal of this clinical trial is to learn the safety of the addition of PULSAR radiation to standard of care chemotherapy and immunotherapy in people with esophageal and gastroesophageal junction cancer and to determine the safest dose of radiation that can be used. Participants in this study will be undergoing clinically scheduled procedures. In addition to the standard of care visits and treatments, there will be additional visits and assessments with radiation.