ATLANTA, GA, October 6, 2004 -- Cancer treatment specialists reported yesterday that a new imaging technology for tracking tumor motion has the potential to improve outcomes and lower complications for many patients. A group of prominent clinicians who recently became the first in the world to use the new On-Board Imager(tm) device from Varian Medical Systems (NYSE: VAR) to treat cancer patients, offered their observations at a “Dynamic Targeting(tm) IGRT” symposium. The presentations were sponsored by Varian in connection with the annual meeting here of the American Society for Therapeutic Radiology and Oncology (ASTRO).
Addressing an audience of approximately 800 radiation therapy professionals, the presenters, Professor Ingemar Naslund, of the Karolinska University Hospital in Stockholm; Yoshiya Yamada, M.D., of Memorial Sloan-Kettering Cancer Center in New York; and Ian Crocker, M.D. and Timothy Fox, PhD, of Emory University Hospital in Atlanta offered details of their early clinical experience with this new technology for image-guided radiation therapy (IGRT), and views on Varian’s cone-beam CT technology option, which is currently pending FDA 510(k) clearance.*
IGRT at Karolinska University Hospital in Stockholm, SwedenProfessor Ingemar Naslund, M.D., PhD, reported on his institution’s use of the Varian On-Board Imager device to decrease the margin of normal tissue surrounding a tumor that is traditionally irradiated during radiotherapy in order to compensate for tumor position uncertainties. He and his clinical colleagues have used the On-Board imager to visualize the tumor area on a daily basis, reducing the dose going to normal tissues, while actually increasing the dose to the tumor. Karolinska was the first clinic in the world to use a Varian On-Board Imager, and it has become a vital tool—one that will be instrumental in future developments in radiotherapy,” Dr. Naslund said.
In addition, Dr. Naslund described two new devices he and his colleagues have developed for use with Varian’s On-Board Imager.“ One is a new marker for placement in the tumor,” he said, that will enable his clinic to take advantage of a “marker matching” feature of the On-Board Imager. The second is a special tilting tabletop that enables him to position patients both vertically (standing) and horizontally for extracranial stereotactic treatments.“ The next step will be developing our ability to check the tumor position in three dimensions using the On-Board Imager for cone-beam CT scanning,” Dr. Naslund said.
Image-Guided Radiotherapy at Memorial Sloan-Kettering Cancer Center
Dr. Yamada’s presentation covered protocols being developed, at Memorial Sloan-Kettering Cancer Center, for using the On-Board Imager to position patients for IMRT treatments.In addition, Dr. Yamada talked about his research into ways of using the On-Board imager to generate cone-beam CT, or three-dimensional, images of a tumor site, just prior to treatment.
“Varian has an excellent tool for generating cone-beam CT images,” Dr. Yamada says about his research using Varian’s cone-beam technology option. “This can potentially be a valuable complement to automated radiographic and fluoroscopic IGRT. At Memorial Sloan-Kettering, we are researching how and when the use of cone-beam CT imaging can make a difference for patients, and looking particularly at stereotactic or hypofractionated approaches to treating tumors that are very close to dose-sensitive structures—for example, paraspinal tumors or prostate cancer.”
According to Dr. Yamada, the precision of Varian’s on-board imaging technology, coupled with the benefits of IMRT, provide clinicians with an extremely powerful tool in the anti-cancer arsenal.
“At our institution, we feel that image-guided therapy has the potential to revolutionize how radiation therapy is conceptualized and delivered. Currently, image-guided radiotherapy of paraspinal lesions has changed the pattern of practice within the spine tumor group at MSKCC.We plan to implement on-board imaging based protocols across a wide spectrum of disease sites.”
Using the On-Board Imager at Emory University
Drs. Fox and Crocker discussed the problem of tumor motion over a four to six week course of daily radiation therapy treatments.Tumors move around within the body by as much as a few centimeters each day due to normal physiological processes and tiny differences in how patients are set up for treatment. Dr.Crocker and Dr. Fox talked about using the On-Board imager to automatically correct for this “inter-fraction motion” between daily treatments, increasing their targeting precision.
“We are using the On-Board Imager system to position more than twenty patients each day,” Dr. Fox reported. “The process adds an average of four or five minutes to each treatment session.” The Emory team reported that, using the On-Board Imager, they find they need to make millimeter shifts in patients’ positions nearly every day. In addition, during the last week of September 2004, Dr. Crocker and Dr. Fox became the first clinicians in the world to treat patients using Varian’s new Trilogy(tm) linear accelerator, which is outfitted with an On-Board Imager device. In the week prior to the ASTRO meeting, they used the new Trilogy machine to deliver stereotactic radiosurgery to a handful of patients with brain lesions.
“The Trilogy system is calibrated to give us a very tight isocenter,precise enough for both intracranial and extracranial radiosurgery,” Dr.Crocker observed. “When we combine that precision with image-guided tumor localization using the On-Board Imager, we have a very effective technology for treating cancer with stereotactic radiosurgery.”
The use of the Trilogy system will soon broaden at Emory. “Moving towards frameless radiosurgery for intracranial tumors is the next step at Emory,” said Dr. Crocker. “We also plan on doing frameless radiosurgery for tumors in other parts of the body by the end of the year.”
* Varian’s cone-beam CT technology option is not currently available for