Radiation Therapy (RT)

This phase II trial studies how well radiation therapy works for the treatment of gastrointestinal cancer that are spreading to other places in the body (metastatic). Radiation therapy uses high energy x-rays to kill cancer cells and shrink tumors. This trial is being done to determine if giving radiation therapy to patients who are being treated with immunotherapy and whose cancers are progressing (getting worse) can slow or stop the growth of their cancers. It may also help researchers determine if giving radiation therapy to one tumor can stimulate the immune system to attack other tumors in the body that are not targeted by the radiation therapy.