Cancer treatment specialists
reported yesterday how new technologies are enabling them to provide
faster, more accurate cancer treatments than was possible with earlier
generations of radiotherapy technology. In presentations given at an
"Emerging Technologies" Symposium sponsored by Varian Medical Systems
(NYSE: VAR) in connection with the annual meeting of the American Society
for Therapeutic Radiology and Oncology (ASTRO), doctors detailed how they
are using RapidArc(TM) radiotherapy technology, as well as cone-beam CT
(3-D) imaging to offer their patients highly-accurate and more comfortable
cancer treatments.
The symposium presentations began with Clif Ling, PhD, a renowned
expert in the fields of medical physics and radiation oncology. In his talk
entitled "Affirming the past -- anticipating the future -- comments during
the 50th Anniversary of ASTRO" he provided a history of the technological
advances, many of which were provided by Varian, that have led to improved
clinical outcomes and increased survival among cancer patients treated with
radiotherapy. According to Ling, the technical advances in radiation
oncology can be summarized in four categories:
1) Improvements in imaging, which made it possible to see a tumor and its
surrounding normal tissues, and to create treatment plans based on a
patient's unique anatomy.
2) Advances in the design and optimization of treatment plans, thanks to
computer algorithms that work with volumetric (3-D) CT image data to
calculate an optimal way of delivering the desired radiation dose in
three dimensions.
3) Improvements to treatment delivery systems, including sophisticated
multileaf collimators that continually shape the radiation beam so it
matches the shape and size of the tumor from all angles.
4) Greater understanding of the clinical radiobiology of radiotherapy, an
effort that continues and that is leading to new studies in the
"uncharted waters" of stereotactic radiotherapy and radiosurgery,
involving very high dose treatments delivered in just one to five
treatment sessions.
The Promise of RapidArc
Using Varian's RapidArc radiotherapy technology in the treatment of
brain tumors, Ben Slotman, who is professor and chairman of the Department
of Radiation Oncology at the VU University Medical Center in Amsterdam,
Netherlands, said he was able to shorten his treatment protocols by an hour
or more per patient. Slotman delivered whole-brain radiotherapy plus an
integrated stereotactic boost in five sessions that took fifteen minutes
per day from start to finish (including imaging, patient positioning, and
treatment). "The main benefit to integrating the stereotactic boost by
using RapidArc is the fact that the patient does not have to lie still for
an additional 60-90 minutes," Slotman said.
"The delivery of a RapidArc treatment is very fast, which has important
clinical implications," he added. "Treatment times are much shorter, so
there is less chance that a patient will move during treatment, which helps
to ensure accurate targeting. Another clear benefit is that it is more
comfortable for patients and more patients can be treated in a single day,"
he said.
Slotman and his colleagues compared RapidArc treatment plans with plans
for conventional IMRT. The RapidArc plans were faster to create, he said,
and they produced equal or better dose distributions with superior
protection of surrounding healthy tissues.
Advances in Image-Guided Radiosurgery with the Novalis Tx Platform
Three-dimensional cone-beam CT imaging is enabling Benjamin Movsas, MD,
to offer his patients image-guided stereotactic radiotherapy and
radiosurgery treatments without the invasive process of planting fiducial
markers, such as gold seeds, into the tumors. Using the On-Board Imager(TM)
device on a new Novalis Tx(TM) treatment platform, Movsas and his clinical
team can generate 3-D images that show soft tissue structures, such as the
tumor and surrounding organs, making fiducial markers unnecessary.
"It's often not possible to place fiducial markers into lung tumors
without risking the possibility of a collapsed lung or other injury," said
Movsas, who is chairman of the Department of Radiation Oncology at Henry
Ford Hospital in Detroit. "Even when fiducials can be safely used, a
cone-beam CT image is still critical because it shows us key information
about the tumor itself, like changes in the tumor volume or shape over
time."
In addition to the On-Board Imager, the Novalis Tx platform at Henry
Ford Hospital in Detroit incorporates ExacTrak(R) room-based X-ray imaging
system, and having both offers some key advantages, Movsas said. "While
cone-beam CT can provide us with in depth data about the targeted tumor,
ExacTrak can be used strategically, to take a "snap shot," even during
treatment, for a rapid verification that the tumor is still in the correct
position."
Movsas, also spoke of the sophisticated stereotactic body radiosurgery
(SBRT) work that has been taking place at Henry Ford for some time, using
earlier generations of linear accelerators from Varian and BrainLAB. Henry
Ford clinicians have treated thousands of patients with focused
stereotactic radiosurgery, and they have become known for their pioneering
clinical work treating tumors of the spine. The new Novalis Tx is being
used to build on this expertise, and to help create a more fully integrated
multidisciplinary stereotactic radiosurgery program.
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
4,800 people who are located at manufacturing sites in North America and
Europe and approximately 60 sales and support offices around the world. For
more information, visit varian.
Varian Medical Systems, Inc.
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