Stockholm-based Elekta has begun clinical trials on its Unity machine, which combines a linear accelerator and high-field magnetic resonance imaging (MRI) to better define and track tumors during radiation treatments. The company believes this new iteration of radiotherapy will be more precise.
“Elekta Unity enables high-quality soft tissue imaging that provides greater information, allowing more effective clinical decision-making,” said Kevin Brown, global vice president of scientific research, in an email. “The precise visual differentiation of tumor from nearby healthy tissue allows clinicians to confidently see and track the exact location of a tumor in real time.”
The challenge with radiation, and other cancer therapies, is getting the right amount of treatment to the tumor and leaving healthy cells unscathed. Image-guided technologies have fueled the evolution towards more targeted radiotherapy. Still, CT imaging adds ionizing radiation and cannot always delineate tumors from surrounding tissue.
Replacing CT with MRI could address both issues, but has been technically challenging. High-powered magnets don’t always play nice with photon radiation, often altering its path. Recent refinements by Elekta, ViewRay and others have made MRI-guided radiation therapy possible, which could be a great benefit for patients.
“I think the MRI-based linear accelerators have a few advantages over CT-guided accelerators,” said Ray Lin, medical director of Scripps Radiation Therapy Center in San Diego during a phone interview. “They better define the soft tissue, so if you’re treating prostate cancer or head and neck cancer, you can see the cancer a little better. Because the tissue is better defined, we could potentially give higher doses with less margin.”
MRI may offer other advantages, such as improved motion management – no small thing when treating lung tumors. And since the imaging technology adds no radiation, it could give clinicians more flexibility to readjust parameters midway through treatment.
“Occasionally we do adaptive planning,” said Lin, “we change the plan based on the shrinkage of the tumor. You can’t do it too much because every time you do a new plan, the patient is exposed to more radiation.”
Despite these potential advantages, Unity may not be the best system for all patients – pacemakers and MRIs don’t mix. However, Elekta believes Unity will augment current linear accelerators, providing added precision for more complex cancers.
For now, the Elekta MR-linac Consortium, which includes MD Anderson Cancer Center in Houston and Froedtert Hospital in Milwaukee, is gathering data, publishing a series of studies on MRI and linear acceleration. In May, as part of a clinical trial, the University Medical Centre Utrecht treated its first patient with Unity. The company expects other sites to begin trials as well, and Unity may be poised for regulatory approval.
“We intend to submit for CE mark approval of Elekta Unity in the second half of 2017,” said Brown, “followed with filing of FDA 510(k) with estimated clearance in 2018.”
Original Author: Josh Baxt
Original Date: Jul 13 2017