Testing the Addition of an Antibody to Standard Chemoradiation Followed by the Antibody for One Year to Standard Chemoradiation Followed by One Year of the Antibody in Patients With Unresectable Stage III Non-Small Cell Lung Cancer

This phase III trial studies how well an antibody (durvalumab) with chemotherapy and radiation therapy (chemoradiation) works in treating patients with stage III non-small cell lung cancer that cannot be removed by surgery (unresectable). Immunotherapy with monoclonal antibodies, such as durvalumab, may help the body`s immune system attack the cancer, and may interfere with the ability of tumor cells to grow and spread. This study is being done to see if adding durvalumab to standard chemoradiation followed by additional durvalumab can extend patients life and/or prevent the tumor from coming back compared to the usual approach of chemoradiation alone followed by durvalumab.