A feasibility study of MRI-guided steriotactic ablative radiotherapy to abdomino-thoracic targets

This study aims to test the feasibility and suitability of the Magnetic Resonance Linear Accelerator (MR Linac) for the delivery of stereotactic ablative radiotherapy (SABR) for patients with cancers in the abdomen and lung. Over the past two decades SABR has been used increasingly for treatment of tumours of the liver, pancreas, kidney and lung. SABR delivers radiation in a high dose per fraction, usually on alternated days, that is precisely delivered, reducing the need for patients to attend 20+ treatments, whilst ablating the tumour or residual disease. NHS England has recently commissioned this type of treatment in a number of these tumour sites. However challenges remain in delivering the most precise treatment as the tumours are difficult to see or distinguish from normal tissues using xray based imaging that is available on standard treatment machines. A second challenge is that these tumours move and change shape as a result of breathing or digestive motion. These changes can happen within a treatment or from day to day. The MR Linac has superior imaging with the ability to gate and adapt treatments in real time. These tools could be used to reduce normal tissue toxicity whilst increasing target doses safely. We propose an observational study using published guidelines for SABR prescriptions to see if patients can tolerate MR-Linac based treatments. We will use the images acquired to investigate: safe dose escalation; real-time adaptation strategies; imaging that could give us information about geometric tumour and normal tissue changes; how the target and normal tissue respond to treatment using special imaging techniques like diffusion weighted- or oxygen-enhanced MRI.