A new technique has the potential to speed up radiotherapy planning for head and neck cancers by skipping over cumbersome and time consuming tasks, while still ensuring treatment is delivered accurately.

Researchers at the Institute of Cancer Research, London, and the Royal Marsden NHS Foundation Trust have developed what they describe as a "halfway" form of adaptive radiotherapy that automates external contour changes on MR Linacs and eliminates the need for clinicians to manually perform target and organ-at-risk recontouring daily. They have dubbed their approach, "ATS-Lite."

Adaptive radiotherapy enables clinicians to account for alterations in tumor shape and position, which commonly change during treatment, to ensure radiation is administered accurately. On MR Linacs, the two most popular methods of this care are adapt-to-position (ATP) and full adapt-to-shape (ATS). But ATP only updates the patient's position, making it less accurate and often requiring off-line replanning. Full ATS requires the patient to remain still for long periods of time and for clinicians to be present daily to perform recontouring. To date, it is unfeasible.

In a study, the scientists used the technique on Elekta's Versa HD linear accelerator and found that ATS-Lite delivered 99.9% of treatment accurately. With it, treatment for one cancer patient was 40 minutes, nine seconds and for another, 32 minutes and 14 seconds. ATP, meanwhile, took an average of 46 minutes and had a higher rate of plan failure by not passing 7.6% of dose constraints. The higher chance of plan failure and extra time needed were chalked up to repositioning the patient more frequently.

The scientists say that any additional benefits from full ATS would be minimal compared to ATS-Lite, and believe their approach could help increase the use of MR Linac for head and neck cancers globally, as well as make treatment simpler and faster. “The ATS-Lite approach will help us perform daily adaptive radiotherapy in a simpler and more efficient way, enabling us to move on from a ‘one size fits all’ approach and helping to increase cure rates and reduce side effects,” said study author professor Kevin Harrington, head of the division of radiotherapy and imaging at The Institute of Cancer Research, London and a consultant oncologist at The Royal Marsden NHS Foundation Trust, in a statement.

A few hospitals across the MR Linac consortium have begun using the approach. The researchers plan to further test ATS-Lite in the coming months and are working with their international colleagues within the consortium to gather data to develop evidence-based treatment. “Testing will include assessing advanced imaging on the MR Linac to guide whether we can safely decrease the radiotherapy dose, which could help to reduce side effects, or escalate treatment if the patient isn’t responding sufficiently," said study leader Dr. Kee Howe Wong, consultant clinical oncologist at the Royal Marsden NHS Foundation Trust.

The research was funded by Cancer Research UK.

The findings were published in Clinical and Translational Radiation Oncology.