Markerless Image Guidance Using Intrafraction Kilovoltage X-ray Imaging

Inclusion Criteria: * Is willing to comply with all trial procedures and intends to provide written Informed Consent for participation in this trial. * Patients undergoing external beam radiotherapy. * Histologically proven Stage I NSCLC or oligometastatic lung metastases (3 or less). * MRI/4D-CT prior to insertion of fiducial markers. * Patient must be able to have fiducial markers placed in the lung (if on anticoagulants, must be cleared by LMO or cardiologist). * ECOG performance status 0-2. * A maximum of three metastases to the lung from any non-haematological malignancy. Multiple metastases will be treated separately. * 1 cm ≤ Tumour diameter in any dimension ≤ = 5 cm. * The distance between the tumour centroid and the top end of the diaphragm is \<=10 cm. Exclusion Criteria: * Patient has low respiratory performance as evaluated by the physicians. * Previous high-dose thoracic radiotherapy. * Less than one fiducial marker implanted in the lung. * Fiducial markers are too far from the tumour centroid (\>9 cm). * Cytotoxic chemotherapy within 3 weeks of commencement of treatment, or concurrently with treatment. Hormonal manipulation agents are allowable (e.g. aromatase inhibitors, selective oestrogen receptor modulators, and gonadotropin releasing hormone receptor modulators). * Targeted agents (such as sunitinib, bevacizumab and tarceva) within 7 days of commencement of treatment, or concurrently with treatment. * Women who are pregnant or lactating. * Unwilling or unable to complete quality of life questionnaires.