1. McGraw, Mark

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Researchers from the Institute of Cancer Research and The Royal Marsden NHS Foundation Trust have used a new adaptive radiotherapy technique that might deliver treatment for head and neck cancers (HNC) in a way that's faster and more accurate than current methods.

MRI. MRI... - Click to enlarge in new windowMRI. MRI

The investigators outlined the technique in a study published in the journal Clinical and Translational Radiation Oncology, where they noted that the Elekta Unity MR-Linac (MRL) MRI scanner has enabled adaptive radiotherapy (ART) for patients with head and neck cancers (2021; Adapt-To-Shape-Lite (ATS-Lite) "is a novel Adapt-to-Shape strategy that provides ART without requiring daily clinician presence to perform online target and organ at risk (OAR) delineation," the authors wrote.


For this study, researchers compared the performance of their clinically delivered ATS-Lite strategy against three Adapt-to-Position (ATP) variants: Adapt Segments (ATP-AS), Optimise Weights (ATP-OW), and Optimise Shapes (ATP-OS). The authors sought to report the technique's result, administering radical dose radiotherapy on the MRL to two patients with head and neck cancer.


For each fraction, an ATS-Lite plan was generated online and delivered, with additional plans being generated offline for each ATP variant. To assess the clinical acceptability of a plan for every fraction, 20 clinical goals for targets and OARs were assessed for all four plans.


Primary tumors and involved nodes received 65 Gy, and nodal regions at risk of harboring microscopic disease received 54 Gy in 30 fractions over 6 weeks. Overall, 53 fractions were analyzed. ATS-Lite passed 99.9 percent of mandatory dose constraints. ATP-AS and ATP-OW each failed 7.6 percent of mandatory dose constraints. The planning target volumes for 54 Gy were the most frequently failing dose constraint targets for ATP.


"Our early data show that the novel ATS-Lite strategy produced plans that fulfilled 99.9 percent of clinical dose constraints in a time frame that is tolerable for patients and comparable to ATP workflows," the researchers wrote. "Therefore, ATS-Lite, which bridges the gap between ATP and full ATS, will be further utilized and developed within our institute, and it is a workflow that should be considered for treating patients with HNC on the MRL."


The current standard of practice for radiation treatment for head and neck cancers utilizes a linear accelerator, which "traditionally [does] not allow good assessments of tumor response during therapies," stated Amit Gupta, MD, a researcher in the Head and Neck Unit at the Royal Marsden NHS Foundation Trust and the Institute of Cancer Research, and a co-author of the study. "It also doesn't readily allow adaptation of treatments once started, as we cannot image the tumor adequately. We only tend to change radiotherapy plans if a patient loses significant weight once treatment has started."


The development of an MR-Linac, which combines a linear accelerator with an MRI scanner, provides an opportunity to visualize the tumor on a daily basis during treatment, "because we can get better soft tissue definition with an MRI scanner," he continued. "This also provides an opportunity to adapt treatment to changes in patient shape (due to weight loss) or tumor response, as a new radiotherapy plan is generated each day."


Thus, having access to an MR-Linac has enabled Gupta and his colleagues to develop a treatment pathway that allows for treating patients with a high degree of accuracy, and in a timeframe that is very tolerable for patients.


The ATS-Lite protocol was designed to be both accurate and as quick as possible, by automating the radiotherapy planning process as much as possible. "The standard protocols that people use to treat on an MR-Linac were either not accurate enough (ATP) or took too long to delivery and were resource-heavy (ATS)," Gupta noted. "Our ATS-Lite protocol combined the benefits from both treatment protocols by being both accurate and of a shorter duration."


Gupta is quick to note, however, that this only applies to treatments on the MR-Linac platform, as the standard linear accelerators use a different delivery protocol. MR-Linac treatments generally take longer due to the generation of a new radiotherapy plan each day, unlike the standard linear accelerator, where the same plan is delivered each day.


In terms of how this new radiotherapy technique could ultimately impact the way radiology teams treat head and neck cancers, Gupta is optimistic that it could provide faster, accurate treatment that is easier for patients to tolerate.


"Going forward, we have continued to treat more patients with head and neck cancers on the MR-Linac, using our ATS-Lite protocol, as well as investigating ways that cancers are responding to radiation treatment early on," Gupta stated. "The MR-Linac platform will allow us the opportunities to combine early assessments of tumor response and adapting to how we can change our radiation treatment at much earlier stages in patients' therapies in attempt to improve overall outcomes."


Mark McGraw is a contributing writer.