Inclusion Criteria:

• Histological confirmation of small cell and non-small cell carcinoma of the lung receiving thoracic radiotherapy > 45 Gy, with volume of lung receiving 20 Gy or more (V20Gy) ≥ 20%
• Eastern Cooperative Oncology Group (ECOG) performance status (PS) 0, 1 or 2
• Absolute neutrophil count (ANC) ≥ 1500/mm^3
• Platelet count ≥ 100,000/mm^3
• Hemoglobin > 9.0 g/dL
• Creatinine clearance ≥ 30 mL/min as calculated using actual body weight and Cockroft Gault formula
• Initial physical exam with systolic blood pressure (BP) of > 100 mmHg and diastolic BP of > 60 mmHg
• Potassium within institutional normal limits
• Sodium within institutional normal limits
• Negative pregnancy test done ≤ 14 days prior to registration, for women of childbearing potential only
• Ability to complete questionnaire(s) by themselves or with assistance
• Provide informed written consent
• Willing to return to enrolling institution for follow-up (during the active monitoring phase of the study)
• Willing to provide blood samples for correlative research purposes

Exclusion Criteria:

• Co-morbid systemic illnesses or other severe concurrent disease which, in the judgment of the investigator, would make the patient inappropriate for entry into this study or interfere significantly with the proper assessment of safety and toxicity of the prescribed regimens
• Uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements
• Other active malignancy ≤ 3 years prior to registration; EXCEPTIONS: Non-melanotic skin cancer or carcinoma-in-situ of the cervix; NOTE: If there is a history or prior malignancy, they must not be receiving other specific treatment (e.g., maintenance or adjuvant chemotherapy or hormonal therapy) for their cancer
• History of myocardial infarction ≤ 6 months prior to registration, or congestive heart failure requiring use of ongoing maintenance therapy for life-threatening ventricular arrhythmias History of prior radiation therapy treatment to the lungs or thorax
• Existing contraindications to angiotensin-converting enzyme (ACE) inhibitors such as hypersensitivity to ACE inhibitors, bilateral renal artery stenosis, angioedema, or previously documented adverse drug reaction to ACE inhibitors
• Any of the following:
  • Pregnant women
  • Nursing women
  • Men or women of childbearing potential who are unwilling to employ adequate contraception
• Use of ACE inhibitors (including lisinopril) or ACE receptor blockers (ARB) of any kind ≤ 90 days prior to registration