Lung cancer is one of the leading causes of death worldwide, and it is the largest contributor to new cancer diagnoses (12% of total new cancer cases) and to death from cancer (18% of total cancer deaths). There are two major groups of lung cancer that arise from the cells of the respiratory epithelium: non-small-cell lung cancer (NSCLC) and small-cell lung cancer, accounting for approximately 85% and 15% of lung cancer cases, respectively. The 5 year survival rate is 70-85% for localized NSCLC, and approximately 10% for metastasized NSCLC. Although surgery is still the standard treatment for early stage lung cancer for operable patients, stereotactic body radiotherapy (SBRT) has emerged as an alternative treatment option, especially for pa...