7. Patients with medically inoperable stage I disease (T1 or T2a [tumor size </=5 cm] N0M0) or selected stage IIa disease (T2 [tumor size >5 cm but </=7 cm] N0M0) who have poor lung function or other significant cardiovascular or other comorbidity such as diabetes are eligible. Patients with operable disease who choose to have SABR are also eligible. The standard justification for medical inoperability is based on pulmonary function and can include any of the following: baseline FEV1 <50% of predicted value; diffusion capacity <50% of predicted value; baseline hypoxemia or hypercapnia; exercise oxygen consumption <50% of predicted value; severe pulmonary hypertension; severe cerebral, cardiac, or peripheral vascular disease; and severe chronic heart disease.