Around 40 per cent of all cancer patients undergo radiotherapy, according to Cancer Research UK, which requires them to have a CT or MRI scan before treatment. The image created by the scan is then used to guide x-ray beams to a tumour within the body. However, both the tumour and surrounding organs may well have changed in position between scanning and start of treatment.

As a result, radiation is generally applied using relatively large safety margins in order to ensure appropriate doses to the tumour, but this approach damages more healthy tissue, causing long-term side effects. For example, women with breast cancer have been known to develop heart conditions as a result of radiation damage. However, this could be decreased substantially with new technology.

The Magnetic Resonance Linear Accelerator (MR Linac) could radically improve success rates for patients and reduce the side effects. By combining two technologies – an MRI scanner with a linear accelerator – the system provides soft-contrast imaging throughout treatment, giving clinicians complete, real-time visibility of a tumour so they can direct x-ray radiation beams at it accurately, even as it moves.

The accuracy that the MR-Linac brings is revolutionary and is a particularly important breakthrough for treating cancers such as lung, prostate, pancreas, bowel and liver, where the tumours often change position between scanning and treatment, and during treatment for instance due to breathing.

 

Real-time, precise treatment

 

“The main benefits come from the fact that you have real-time guidance during treatment delivery,” explains Dr Frank Lagerwaard, Radiation Oncologist at the VU University Medical Center in Amsterdam, who has been working with a similar MRI-guided radiation therapy system. “Now that we can see what we are doing, we only need very small safety margins, and can even treat during breath-hold, resulting in very precise treatment delivery with much less radiation to surrounding healthy tissues.”

"Usually we deliver radiation with a very generous safety margin."

“Typically we plan for an entire series of radiation fractions assuming that the situation in the patient doesn’t change,” continues Lagerwaard. “The new system allows you to perform MR imaging prior to each fraction, so you can optimise your treatment plan for each fraction of radiation delivery, a process called adaptive radiotherapy. This ensures optimal radiation delivery for virtually all fractions and increases the safety of critical organs.”

The MR Linac doesn’t simply require new procedures of operation; it will require clinicians to work in new ways, too. Currently, oncologists aren’t present during the treatment delivery process, which is managed by technicians. With real-time scanning, that will all change and the oncologists will be required to assess imaging prior to and during delivery of the treatment, thus actually be present at the treatment machine.

 

Extra staff – and money – required

 

The system certainly has the power to revolutionise radiotherapy, but there are some limitations. There are currently very few machines in clinical use and the whole procedure requires extra staff and time which, of course, costs money. However, in the long run there could be cost savings as more accurate treatment will reduce the need for multiple patient visits, and possibly a reduction in also costly side-effects.

“Imaging, plan optimalisation and delivery for a single fraction at this moment can mount up to 30 minutes for prostate cancer or 45 minutes for upper abdominal lesions. If you want to do this for 30 fractions, for instance, it will be way too time consuming for departments and patients,” explains Lagerwaard. “Theoretically, it could benefit all patients undergoing radiotherapy, but at this moment we need to select our patients carefully.”

Technology is advancing at such a rapid pace and Lagerwaard is confident it won’t be too long before MRI-guided radiation therapy systems become the norm in hospitals across the world.