Risk Adapted SABR(SABR) in Stage I NSCLC And Lung Metastases

Inclusion Criteria: * Histologically-confirmed primary lung cancer or lung metastasis from another primary tumour or positive PET/CT suggestive for primary tumour(SUV MAX\> 4). * Tumour size \< 5 cm in diameter prior to treatment. * Medically inoperable patients as determined by the multidisciplinary thoracic tumour board, or medically operable patients who refuse surgery. * Life expectancy of \>12 months. * Criterion for medical inoperability include: Overall clinical assessment at the UCLA thoracic tumour board. Reduced Pulmonary Function (FEV1, DLCO, etc) based on one major or two minor criterion as described below: Minor Criteria: Age \> 75, FEV1 51- 60% predicted, or FEV1 1-1.2L, DLCO 51%-60% predicted, pulmonary hypertension, poor left ventricular function (EF \< 40% or less), resting or exercise arterial pO2 \< 55 mmHg, and pCO2 \> 45 mmHg. * Age \> 18 years. * KPS \> 70. * Barthel score \>40 * Baseline computed tomography scans of the chest, pulmonary test function, and positron emission tomography no more than 2 months before treatment. * If a woman is of childbearing potential, a negative urine or serum pregnancy test must be documented. * Ability to understand and the willingness to sign a written informed consent. Exclusion Criteria: * Prior thoracic radiation treatment wich dose contribution can be expected in the new SBRT plan. * More than two lesions per lobe. * Active infections requiring systemic antibiotics. * Age \<18 years old. * KPs \< 70. * Barthel Total Score \< 40.