The UK’s first MRIdian MR linacs
Treating tumours of the kidney with radiation can be difficult as normal breathing means that the target area moves and the kidneys are positioned near to loops of bowel. Magnetic resonance image guided radiotherapy (MRIgRT) is the most exciting development in advanced radiotherapy for years. MRIgRT provides a step-change in accurate stereotactic ablative radiotherapy (SABR) for renal cell carcinoma (RCC), bringing a new level of control and confidence with tumour targeting and the sparing of normal tissue, such as the other kidney, small and large bowel and spinal cord. This is because it allows clinicians to treat only when the targeted area is completely within the radiation field.
We’re proud to be the first independent healthcare provider in the UK to introduce the MRIdian – an advanced MR linac. This world-class radiotherapy system is available at our centres in Oxford and Cromwell Hospital in London and can be accessed by patients throughout the UK. By combining a linear accelerator with a high-definition MR scanner, MRIdian allows clinicians to see as they treat, adjusting the beams to allow for movements and anatomical changes every day and delivering the radiotherapy dose only when the tumour is positioned in the treatment window. No other machine in the UK is currently able to achieve all this. MRIdian makes truly adaptive SABR possible for the first time.
Benefits for renal cell carcinoma patients
SABR for renal cancer is rapidly becoming established as an alternative to the more invasive options of nephrectomy or percutaneous ablative therapies. The MRIdian’s combination of advanced technologies makes it possible to safely treat a wider range of tumour sizes, with higher-doses and in fewer treatment sessions which range from one to five depending on the clinical scenario. MRI-guided SABR does not require additional invasive procedures to either place gold beads (fiducial markers) or make permanent tattoos that are required for body positioning on conventional non-MRI-guided SABR machines.
Concomitant health problems may mean surgery is inadvisable or simply not possible for some RCC patients or the patient may prefer to not have surgery. Treatments that are less invasive than surgery, such as percutaneous ablation are available. However, these are often limited to the treatment of smaller tumours or, with larger tumour sizes, pose greater risk of damage to the surrounding organs, as well as requiring a general anaesthetic.
Occasionally the position of the tumour in the middle of the kidney may mean ablative procedures are not recommended and the option of a partial nephrectomy is not available. SABR therefore may allow the treatment of the tumour without having to resort to the loss of an entire kidney.
Patients receiving SABR to the kidney can typically experience mild tiredness, nausea which responds well to anti-emetics, and a drop in renal function.
MRI-guided SABR is a high-precision, non-invasive radiation treatment delivered in only a few outpatient visits. It represents a safe and effective management option for patients with primary RCC unable to undergo surgery, with excellent local control rates. It also offers a reduced risk of possible toxicity which may otherwise be caused, as well as a reduced risk of diminished renal function when compared to surgery.
Our centre in Oxford is rated ‘Good’ by the Care Quality Commission (CQC).
A new paradigm in radiation oncology
Real-time, on-table, adaptive radiotherapy brings a new level of confidence to SABR delivery
MRI-guided radiotherapy improves on conventional image-guided radiotherapy (IGRT) by providing enhanced soft tissue definition without additional radiation exposure through high-quality MR images.
By capturing MR images of the target many times per second, the MRIdian provides real-time, moving images that capture the anatomical position changes that occur naturally within the body. Uniquely, the MRIdian allows tracking of the target position in real time, coupled with a gating facility that prevents beam delivery when the target is outside the treatment boundaries. This level of accuracy means that uncertainty is reduced, eliminating the need for large margins around the target.
The MRIdian has opened up new avenues of treatment, particularly tumours that move and are within close proximity of organs at risk (OAR) such as tumours of the kidney, where high doses are achievable while keeping the doses to OARs within tolerance.
The MRIdian allows clinicians to provide true online adaptive radiotherapy. The treatment planning system is clear and intuitive, making daily re-contouring of tumour and normal tissues straightforward. The updated plans are rapidly re-optimised providing a personalised radiation treatment for each patient on every fraction.
- The MRIdian uses a patented split-magnet MR design so that the radiation beam is not distorted by the magnetic field and is at the optimum distance for exceptionally sharp, high dose-rate SABR
- The MR set-up captures multiple high-definition, high-quality images many times a second, detecting even the slightest movement of the tumour and surrounding organs
- The MRIdian allows the clinicians to perform real-time, on-table plan adjustments to reflect both inter– and intra-fraction anatomical changes or movements
- When the gating target moves outside the pre-specified gating boundary, the radiation beam automatically stops until the target returns back inside the gating boundary
- The gating target and gating boundary are visualised on the display and some patients benefit from being able to view this while inside the MRIdian, thus enabling them to take an active role in gated delivery by adjusting their breathing
- Coupled with the unique target tracking and gating system is a precise stereotactic radiation beam, giving the clinician greater control and confidence in delivering maximal dose to the tumour target while preserving critical structures
Research shows that treatment with SABR allows for a reduction in radiation dose to the surrounding normal tissues, such as the small bowel, spinal cord, large bowel and second kidney , reducing the risk of possible toxicity which may otherwise be caused.
It also offers a reduced risk of diminished renal function in comparison to surgery. This is shown in a study of 95 patients with larger (T1b, >4 cm) renal cell carcinoma, where 77.6% were defined as inoperable by the referring urologist. 38 patients (40%) had a grade 1 to 2 toxicity and no grade 3 to 5 toxicities were reported. Cancer-specific survival, overall survival, and progression-free survival were 96.1%, 83.7%, and 81.0% at two years and 91.4%, 69.2%, 64.9% at four years, respectively .
By using the MRIdian to deliver SABR, we aim to improve on these outcomes by further reducing radiation dose to normal tissues.
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MRIdian specialists at GenesisCare
Patient care on the MRIdian is delivered by a team of specially trained consultant oncologists, selected on the basis of their clinical expertise. Collectively the team provide a comprehensive infrastructure for patient selection, peer review and clinical governance for all referrals as well as the credentialing of new clinicians in MRI-guided radiotherapy. We are excited to be partnering with the University of Oxford to build a body of evidence that will have a positive impact on the lives of many patients.