The purpose of this study is to use SBRT in patients with early stage lung cancer and find out what effects (good and bad) SBRT has on their cancer. This research is being done because SBRT has not been used very often in patients with early stage lung cancer or in patients with other serious health problems. In addition, this study also will gather information about patient's health and hospitalization history. This information will be used to find out if there are any factors that can help predict recovery or outcome of patients with lung cancer.