A Study to Test Lung Function After Radiation Therapy

Inclusion Criteria: * Histological diagnosis of small cell or non-small cell lung cancer or metastatic tumor to the lung being scheduled for localized radiation therapy (including radiosurgery) * No prior or future planned surgery for the treatment of the lung cancer. * Age ≥ 18 years * Karnofsky 60% * Not pregnant. * Ability to understand and the willingness to sign a written informed consent document * Ability and willingness to participate in breathing training and compliance wiht breathing apparatus so that radiation doses are optimally linked to 4D-CT images * Ability to tolerate CT contrast Exclusion Criteria: * No prior thoracic radiotherapy will be permitted * 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 * Pregnant women * Severe COPD that requires chronic prednisone or multiple inhalers * Underlying collagen vascular disease or intrinsic lung disease that could complicate expected sequelae of radiation (idiopathic pulmonary fibrosis, Wegener's granulomatosis) * Oxygen dependence at baseline * Recent lung surgery or abdominal surgery (within 3 weeks) that would compromise respiratory pattern.