Esomeprazole and Radiation Induced Esophagitis

Inclusion Criteria: * Patient is ≥ 18 years of age. * Patient or patient's legal representative is willing and able to provide written informed consent and HIPAA authorization prior to performance of any study related activity. * Patient is willing and able to comply with scheduled visits and treatment schedules. * Patient has histopathologically confirmed diagnosis of NSCLC clinical stage III (as per the 8th edition of American Joint Committee on Cancer Staging). * Patients will receive thoracic radiation with estimated maximum dose to esophagus of at least 30 Gy (EQD2) in combination with concomitant chemotherapy. * Patient has Eastern Cooperative Oncology Group (ECOG) performance status score of 0 to 2. * Women of childbearing potential (WOCBP) must have a negative pregnancy test (serum or urine HCG) within 2 weeks of enrollment). * Double inclusion in any ongoing trial (if the other trial permits) will be allowed. Exclusion Criteria: * Patient has history of gastroesophageal junction or stomach cancer. * Patient has history of pre-existing severe or very severe dysphagia. * Patient has history of severe liver disease, acute or subacute systemic lupus erythematosus. * Patient has interstitial nephritis. * Patient has history of peptic ulcer disease. * Patient has prior history of upper gastrointestinal bleeding. * Patient has a history of thoracic radiotherapy within 2 years of enrollment. * Patient has known or suspected allergic response and prior adverse drug reaction with proton pump inhibitors. * Patient is currently on clopidogrel, nelfinavir, rilpivirine, methotrexate, rifampin, digoxin, tacrolimus, or phenytoin as these may have major drug interaction with esomeprazole. * Patients without concomitant chemoradiotherapy and with estimated maximum dose to esophagus of less than 30 Gy (EQD2).