Stereotactic Body Radiation Therapy in Treating Patients With Stage I Non-Small Cell Lung Cancer

OBJECTIVES: Primary * To determine the maximum tolerated dose (MTD) of stereotactic body radiotherapy (SBRT) in medically inoperable patients with centrally located stage I non-small cell lung cancer. (Phase I) * To estimate the local control rate of SBRT at the MTD in these patients. (Phase II) Secondary * To estimate the rates of adverse events (other than dose-limiting toxicity) of ≥ grade 3 that is possibly, probably, or definitely related to treatment and that occurs within 1 year after the start of SBRT in these patients. * To estimate the rates of late adverse events (i.e., occurs \> 1 year after the start of SBRT) in these patients. * To estimate the local control and progression-free and overall survival rates in patients treated with this regimen. OUTLINE: This is a multicenter study. Patients undergo stereotactic body radiotherapy every 2 days over 1½-2 weeks \[total of 5 fractions (FX)\] in the absence of disease progression or unacceptable toxicity. After completion of study therapy, patients are followed every 3 months for 2 years, then every 6 months for 2 years, then annually.