Stereotactic Body Radiotherapy (SBRT) has emerged as a new treatment option for peripherally located lung tumours, offering very high rates of tumour eradication, with minimal side effects. Even though this treatment option is being adopted in more and more cancer centres, there is still no consensus about the optimal schedule for the radiation treatment. Generally speaking, most lung SBRT schedules involve delivering 3-4 days of radiation. At the Sunnybrook Odette Cancer Centre, the lung SBRT policy is to deliver 4 days of radiation over 11 days (each treatment given once very 3rd day). However, some centres deliver the same treatment over 4 days in a row (each treatment given once daily over 4 days). There is no evidence from the published literature to suggest that there is any difference in side effects between delivering the SBRT over 4 days versus 11 days. To confirm this, the investigators propose to conduct a comparative (randomized) study to compare these 2 approaches.

Inclusion Criteria:

• Pathologic diagnosis of malignancy in the lung (either NSCLC or metastasis)
• If pathologic diagnosis is not available, there must be evidence of FDG uptake on PET-CT suggestive of malignancy and/or evidence of tumour growth over serial CT scans
• Clinical stage I lung cancer or solitary lung metastasis located in the periphery away from central mediastinal structures and <=5cm in size
• Patient deemed suitable for lung SBRT (reasonable performance status, acceptable pulmonary function) by the attending Radiation Oncologist