Researchers working with the TrueBeam system from Varian Medical Systems have reported on breakthrough research that capitalizes on the unique capabilities of this advanced platform to deliver much more concentrated doses of radiation to tumors to potentially achieve better outcomes in the fight against cancer.
The four pi (4π) noncoplanar approach to treatment exploits specific capabilities of the TrueBeam platform to deliver more compact radiation doses that can fully saturate a targeted tumor and "fall off" sharply outside the target zone, minimizing and, where necessary, even eliminating dose to specific organs requiring more protection. It was outlined by Varian consultant Patrick Kupelian, MD, professor of radiation oncology and vice-chair of clinical operations and clinical research at the University of California, Los Angeles (UCLA) via video presentation at Varian's Users Meeting last month.
"We believe this approach could enable High Definition Radiotherapy (HDRT)—the next big advance in radiation oncology, rivaling the development of IMRT in the 1990s, IGRT and volumetric modulated arc therapy (VMAT) in the 2000s, and linac-based radiosurgery in more recent years, in terms of importance to the field and potential impact on patients," said Kolleen Kennedy, president of Varian Oncology Systems. "It has the potential to vastly simplify how advanced treatments like stereotactic radiosurgery are planned and delivered, and may make it possible for more facilities to offer these precise, efficient forms of treatment to more patients. We anticipate that a high definition approach could make image-guided radiosurgery a mainstream offering, for clinical and also for economic reasons."
Varian's vision for High Definition Radiotherapy also involves facilitating the use of different imaging modalities as required, both during the planning stage and for image-guidance during treatment. "We're developing a comprehensive ecosystem around the TrueBeam machine that will enable clinicians to use CT, cone-beam CT, MR, and/or PET images for treatment planning, image guidance, and even for adaptation—whatever is best for each individual patient," Kennedy said.
Research at UCLA Shows the Potential of High Definition Radiotherapy
Dr. Kupelian and his colleagues at UCLA have been testing software that optimizes a treatment using automated delivery of non-coplanar beam angles (ie, angles of approach that are not in a single plane, but that converge on the tumor from many different directions). This allows the clinician to develop a treatment plan that increases the amount of normal organ sparing, and that misses specific areas, such as the heart, brain stem, or spinal cord, altogether.
The UCLA team has published about their work creating treatment plans for lung tumors, demonstrating that, compared with conventional IMRT plans, 4π non-coplanar approaches could significantly reduce the amount of dose going to the heart, esophagus, trachea/bronchus tree, spinal cord, and healthy lung tissues.1 Another published study compared non-coplanar plans with VMAT plans for liver cancer, finding that the former could offer significant improvements in dose conformality and normal organ sparing.2
"UCLA radiation oncology has launched a prospective clinical trial, with Varian support, to test the safety and clinical flow of High Definition Radiotherapy," said Ke Sheng, PhD, medical physicist who, with his colleague Daniel Low, PhD, developed the 4π algorithm being studied at UCLA. "Five patients have now been treated under the protocol, using treatment plans that spared more critical tissues than would have been possible using conventional IMRT."
"Our vision is to enable High Definition Radiotherapy by commercializing the sophisticated software and hardware enhancements that can enable these types of non-coplanar treatments to be implemented using the TrueBeam system," said Kennedy. "The key is the ability to move the treatment couch—with the patient on it—while the treatment machine is rotating around the patient to achieve a dramatic increase in the number of beam angles used to attack the tumor. The dynamically shaped beams will then converge on the tumor from many different directions, providing more options for avoiding critical areas of the patient's body."
"Many of the elements needed for high-definition radiotherapy are present in the TrueBeam system today," Kennedy added. "We are working with clinical research partners around the world to further define and deliver the toolkit that will make it possible to plan and deliver these very sophisticated treatments safely, efficiently and accurately. Enabling high definition radiotherapy is a big focus right now, and it's one of the more important developments our customers can expect from our R&D pipeline in the future."
1. Dong P et al. 4π Noncoplanar Stereotactic Body Radiation Therapy for Centrally Located or Larger Lung Tumors. Int J Radiation Oncol Biol Phys, Vol. 86, No. 3, pp. 407-413, 2013.
2. Dong P et al. 4π Non-Coplanar Liver SBRT: A Novel Delivery Technique. Int J Radiation Oncol Biol Phys, Vol. 85, No. 5, pp. 1360-1366, 2013.