PHILADELPHIA, Nov. 8 /PRNewswire-FirstCall/ -- New image-guidance and tumor motion management techniques are making it possible for clinicians to detect changes in tumor size, shape, position, or metabolism over a course of radiotherapy treatment, and to adapt the treatment strategy accordingly, according to three leading clinical experts who presented at a symposium sponsored here yesterday by Varian Medical Systems (NYSE: VAR). More than 900 radiation oncology professionals attended the symposium on the use of new image-guided radiotherapy techniques to improve the effectiveness of cancer care. The event was held in connection with the annual meeting of the American Society for Therapeutic Radiology and Oncology (ASTRO).
IGRT for Motion Management in the Thorax
Billy W. Loo, Jr., M.D., Ph.D. of Stanford University, Palo Alto, California, focused on strategies for improving the precision of treatments for lung cancer and other thoracic tumors by tracking and compensating for respiratory motion. Loo's team uses image sequences that show the extent of tumor motion in order to plan more precise treatments. The technique enables him to escalate the dose delivered to the tumor while preserving the surrounding healthy tissues. Based on these moving images, Loo works out an optimal geometric approach for putting the tumor into a crossfire of finely-shaped radiotherapy treatment beams. He also is able to use the image sequences with Varian's RPM™ respiratory gating technology to turn on the beams in timed bursts that are synchronized with the patient's respiratory cycle, so that dose is delivered only when the tumor is in the optimal position for treatment.
Loo's team uses Varian's On-Board Imager® device before beginning each treatment session to verify that the planned respiratory gating strategy will give the desired result, which is a high dose delivered to the tumor and very little anywhere else. "We have found that it is important to do a daily image-guided verification of the respiratory gating strategy. Things can change between the time you plan and the moment you deliver a treatment. And there are certainly many changes throughout a multi-week course of treatment."
Using Biological Image Data to Adapt Cancer Treatments
Karin Haustermans, M.D., Ph.D., of the Department of Radiation Oncology at UZ Gasthuisberg in Leuven, Belgium, discussed ways of using functional imaging -- namely, PET-CT and MRI -- to detect radiation-resistant regions in rectal cancer in order to target them with higher radiation doses using image-guided treatment delivery techniques.
"Most relapses in high-risk rectal cancer patients occur in areas that were already treated with radiation," Haustermans said. "The aim of our study was to develop methods of detecting the radiation resistant regions in tumors and target them more aggressively." Haustermans described how tumors changed over time during a course of treatment -- both in size, shape, and metabolic activity. Her team is now comparing different treatment approaches that could be adopted using this information to improve dose distribution and treatment effectiveness.
Hypofractionation for Prostate Cancer
Alan Pollack, M.D., Ph.D., chairman of the Radiation Oncology Department at Fox Chase Cancer Center in Philadelphia, Pennsylvania, is leading a clinical study on strategies for shortening the duration of a course of radiotherapy treatment for prostate cancer, which normally takes up to eight weeks. His approach involves delivering higher doses with greater precision over fewer treatment sessions, as compared with more conventional treatment approaches.
"Giving higher doses per treatment session has potential advantages, but requires very precise targeting of the prostate to avoid the surrounding normal tissues. We are using 3-D imaging daily before each treatment, which allows for reduced exposure of the bladder and rectum to high radiation doses while ensuring that radiation delivery to the prostate and the potential for tumor eradication are optimized," Pollack said.
"It's very gratifying, to learn about how these medical professionals are pioneering new treatments by marshalling new technologies in order to improve the quality of cancer care," said Timothy Guertin, president and CEO of Varian Medical Systems. "We were proud to sponsor an educational event offering radiation oncologists such an exciting glimpse into the future."
ABOUT VARIAN MEDICAL SYSTEMS
Varian Medical Systems, Inc., of Palo Alto, California is the world's leading manufacturer of medical technology for treating cancer and other medical conditions with radiotherapy, brachytherapy, and radiosurgery. The company is also a premier supplier of X-ray tubes and digital image detectors for imaging in medical, scientific, and industrial applications. The company's high-energy imaging systems are also used for screening cargo. Varian Medical Systems employs approximately 3,900 people who are located at manufacturing sites in North America and Europe and in its 56 sales and support offices around the world. For more information, visit http://www.varian.com/.
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SOURCE: Varian Medical Systems, Inc.
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