Scientific Presentations at 2011 AAPM/COMP Meeting Highlight TrueBeam® and RapidArc® Radiotherapy Systems From Varian Medical Systems

VANCOUVER, British Columbia, Aug. 9, 2011 /PRNewswire/ -- Medical physicists researching RapidArc® radiotherapy technology from Varian Medical Systems (NYSE: VAR) have reported that, compared with conventional approaches to radiotherapy, RapidArc treatment plans for lung, abdominal and spinal tumors do a better job of sparing healthy tissues and organs.

Presenting at a professional conference of medical physicists last week, a team from Mount Sinai Medical Center in New York reported that a RapidArc treatment plan for treating a single complex case of lung cancer spared more healthy tissues and critical organs than a treatment plan for IMRT or 3-D conformal radiotherapy.  In this treatment plan comparison study, the average dose to healthy lung tissues was 8 Gy lower for the RapidArc plan as compared with the other two treatment approaches. The amount of healthy tissue receiving 10-20% of the prescribed dose—a common way of measuring how much healthy tissue is being impacted—was 45% to 50% lower for the RapidArc plan, compared to the other two plan types.  In addition, the investigators found the RapidArc plan offered better tumor coverage than the 3-D conformal radiotherapy plan.(1)

"RapidArc for whole abdominal irradiation in patients offers better homogeneity with the same level of kidney sparing while providing more sparing of organs at risk, such as the bone marrow," concluded a team of researchers from North Shore Long Island Jewish Health System, in a poster presentation comparing RapidArc with a more conventional 2-beam approach to whole abdominal radiotherapy for a single patient.  For example, the amount of healthy bone marrow receiving up to 90% of the prescribed dose went from 95.13% with the conventional treatment plan down to 18.4% in the RapidArc plan.(2) Whole abdominal radiotherapy is often prescribed for some gynecological and gastrointestinal cancers.

Clinicians from St. Luke's Hospital in Bethlehem, Pennsylvania, described an approach to RapidArc treatment planning that enabled them to achieve superior dose distributions for treating spine tumors with stereotactic radiosurgery.  Their poster presentation studied the dosimetry characteristics of 11 RapidArc treatment plans for spinal tumors, and concluded that their RapidArc plans "allow for extremely rapid dose fall off," which means that outside the target area, the dose levels drop very quickly to help protect surrounding healthy tissues.(3)

RapidArc delivers a precise and efficient treatment in a single or multiple arcs of the treatment machine around the patient and makes it possible to deliver image-guided radiotherapy treatments two to eight times faster than is possible with conventional approaches such as fixed-field IMRT or 3-D conformal radiotherapy.

The scientific program at the 2011 joint meeting of the American Association of Physicists in Medicine (AAPM) and the Canadian Organization of Medical Physicists (COMP) included other notable presentations and posters:

• Researchers from Memorial Sloan-Kettering Cancer Center in New York presented about a method they developed for imaging patients during RapidArc treatments, using the imager on Varian's TrueBeam system to facilitate real-time image guidance. (4)^*
• A team from Vanderbilt University Medical Center in Nashville, Tennessee, conducted measurement studies to verify that the TrueBeam system's imager can produce 3-D (cone-beam CT) images using less X-ray dose than earlier generations of technology, without compromising image quality.(5)^,*
• Stanford University researchers reported on a quality assurance (QA) method for gated RapidArc treatments designed to compensate for respiratory motion during stereotactic body radiotherapy treatments.  They simulated imaging, treatment planning, and treatment delivery using a moving phantom to verify that gated RapidArc can produce dose distributions that accurately conform to the three-dimensional shape of a targeted tumor even though dose delivery is continually adjusted to compensate for tumor motion during treatment. (6)
• Three research teams reported on the Acuros XB dose calculation algorithm, which was added to Varian's Eclipse™ treatment planning software last year as a faster alternative to Monte Carlo algorithms for planning RapidArc and other complex treatments. A group from the M.D. Anderson Cancer Center in Houston reported on a head and neck cancer case that was planned using diverse calculation algorithms that were then compared.  They concluded that the Acuros XB algorithm makes it possible to complete calculations for a RapidArc treatment plan roughly three times faster than the AAA algorithm.(7) Another M. D. Anderson team used a phantom study to compare the dosimetric performance of Acuros XB with other treatment planning algorithms.  Acuros XB was found to be equivalent to the Monte Carlo (MC) algorithm and superior to the anisotropic analytical algorithm (AAA) and the collapsed-cone convolution (CCC) algorithm.(8)  And a group from the Istituto Oncologico della Svizzera Italiana (IOSI) in Bellinzona, Switzerland performed a treatment planning and phantom irradiation study to validate Acuros XB as a viable algorithm for planning RapidArc stereotactic treatments.(9)^*

"Over 50 presentations and posters at this year's international meeting of medical physicists reported on clinical or scientific work using Varian technology," said Chris Toth, senior director of marketing for Varian's Oncology Systems business.  "Of those, 35 were based on our RapidArc radiotherapy technology, while another eleven looked at ways of using our TrueBeam system for image-guided radiotherapy and radiosurgery.  We're gratified to see so many leading clinical researchers using Varian technology to advance the field of radiation oncology."

Varian high-energy linear accelerators, including the TrueBeam™ machine, have been cleared by the FDA for treating lesions, tumors, and conditions anywhere in the body when radiation treatment is indicated.  Eclipse treatment planning software has been cleared for planning photon, electron, and proton beam radiotherapy for patients with malignant or benign diseases.

About Varian Medical Systems

Varian Medical Systems, Inc., of Palo Alto, California, is the world's leading manufacturer of medical devices and software for treating cancer and other medical conditions with radiotherapy, radiosurgery, proton therapy, and brachytherapy. The company supplies informatics software for managing comprehensive cancer clinics, radiotherapy centers and medical oncology practices. Varian is a premier supplier of tubes and digital detectors for X-ray imaging in medical, scientific, and industrial applications and also supplies X-ray imaging products for cargo screening and industrial inspection. Varian Medical Systems employs approximately 5,700 people who are located at manufacturing sites in North America, Europe, and China and approximately 70 sales and support offices around the world. For more information, visit http://www.varian.com.

^*One or more members of this research team received research grant support from Varian Medical Systems.

FOR INFORMATION CONTACT:
Meryl Ginsberg
Tel: 650.424.6444
[email protected]

(1) Dumane V et al.  Comparison of Rapidarc, IMRT and 3D Conformal Planning for Treatment of Chestwall, and Regional Nodes. Abstract of poster presented at the 2011 Joint meeting of the American Association of Physicists in Medicine (AAPM) and the Canadian Organization of Medical Physicists (COMP), Sunday, July 31, 2011.

(2) Yuen P et al. Phantom and clinical study of whole-abdominal radiation therapy on a TrueBeam linac: a comparison between traditional treatment and volumetric intensity–modulated arc therapy.  Abstract of poster presented at the 2011 Joint meeting of the American Association of Physicists in Medicine (AAPM) and the Canadian Organization of Medical Physicists (COMP), Sunday, July 31, 2011.

(3) Song X et al.  A Study of RapidArc SBRT Spine Treatment Plans. Abstract of poster presented at the 2011 Joint meeting of the American Association of Physicists in Medicine (AAPM) and the Canadian Organization of Medical Physicists (COMP), Sunday, July 31, 2011.

(4) Ling C et al. Concomitant RapidArc® and Acquisition of KV-CBCT with Minimal MV Scatter.  Abstract for a presentation at the 2011 Joint meeting of the American Association of Physicists in Medicine (AAPM) and the Canadian Organization of Medical Physicists (COMP), Monday, August 01, 2011.

(5) Ding G et al.  Reduced CBCT Imaging Dose Due to the New X-Ray Source in TrueBeam.  Abstract for a presentation at the 2011 Joint meeting of the American Association of Physicists in Medicine (AAPM) and the Canadian Organization of Medical Physicists (COMP), Sunday, July 31, 2011.

(6) Hsu A et al.  Quality Assurance of Gated RapidArc Stereotactic Body Irradiation.   Abstract for a presentation at the 2011 Joint meeting of the American Association of Physicists in Medicine (AAPM) and the Canadian Organization of Medical Physicists (COMP), Sunday, July 31, 2011.

(7) Han T et al. Dosimetric Verification of Deterministic Acuros XB Radiation Transport Algorithm for IMRT and VMAT Plans with the RPC H&N Phantom.  Abstract of poster presented at the 2011 Joint meeting of the American Association of Physicists in Medicine (AAPM) and the Canadian Organization of Medical Physicists (COMP), Sunday, July 31, 2011.

(8) Han T et al. Dosimetric Comparison of Acuros XB Deterministic Radiation Transport Method with Monte Carlo and Model-Based Convolution Methods in Heterogeneous Media. Abstract for a presentation at the 2011 Joint meeting of the American Association of Physicists in Medicine (AAPM) and the Canadian Organization of Medical Physicists (COMP), Monday, August 01, 2011.

(9) Fogliata A. Acuros XB and AAA Dose Calculation Accuracy for Small Fields in RapidArc Treatments. Abstract of poster presented at the 2011 Joint meeting of the American Association of Physicists in Medicine (AAPM) and the Canadian Organization of Medical Physicists (COMP), Sunday, July 31, 2011.

SOURCE Varian Medical Systems