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).