Primary Objective: Assess the treatment fidelity for early Durvalumab initiation (i.e., within 14 days after the last day of radiation therapy) following chemoradiation for Stage III, unresectable nonsmall cell lung cancer.~Secondary Objectives:~Assess the treatment fidelity for very early Durvalumab initiation (i.e., within seven days after the last day of radiation therapy) following chemoradiation for Stage III, unresectable nonsmall cell lung cancer.~Assess barriers to earlier Durvalumab initiation following chemoradiation for Stage III nonsmall cell lung cancer.~Describe the toxicity of Durvalumab when initiated quickly after chemoradiation for Stage III nonsmall cell lung cancer as compared to historical controls.~Describe the efficacy of Durvalumab when initiated quickly after chemoradiation for Stage III nonsmall cell lung cancer as compared to historical controls.~Describe the patient-reported outcomes of Durvalumab when initiated quickly after chemoradiation for Stage III nonsmall cell lung cancer as compared to historical controls.
This research study aims to determine what effects (good and bad) Durvalumab has on participants and their cancer with a quick start of Durvalumab within 14 days of finishing chemotherapy and radiation. The study will also determine the logistic barriers to the quick start of Durvalumab.