Experts Detail How Advanced Imaging Technologies Are Changing The Field Of Radiation Oncology | Varian

Experts Detail How Advanced Imaging Technologies Are Changing The Field Of Radiation Oncology

Salt Lake City, UT - October 22, 2003 - New specialized imagingtechniques and intensity-modulated radiotherapy (IMRT) are enabling doctors to
improve radiation treatments for many cancer patients, including
children.  A trio of prominent physicians described their promising
observations at an "Emerging Technologies" symposium sponsored here yesterday
by Varian Medical Systems (NYSE:VAR) in connection with the annual meeting of
the American Society for Therapeutic Radiology and Oncology (ASTRO).

The physicians, Ben Slotman, M.D., PhD, of VU University Medical Center in
Amsterdam, Suzanne Wolden, M.D., of Memorial Sloan-Kettering Cancer Center in
New York, and Clifford Chao, M.D. of M.D. Anderson Cancer Center in Houston,
presented information from their clinical experience with
respiration-synchronized CT scanning, treating pediatric patients with IMRT,
and combining PET and CT scanning for radiotherapy treatment planning. 

Four-Dimensional CT Scanning
"A recent adaptation of CT scanning appears to offer a breakthrough in
situations where respiration-induced tumor motion is a problem," said Dr.
Slotman. The technique, referred to as "four-dimensional CT scanning," enables
physicians to precisely locate a tumor at any point in the patient's breathing
cycle.  The information from four-dimensional CT scanning can be used to
closely target a tumor during treatments in order to spare more healthy
tissue. 

"We can utilize the phase of respiration where the greatest separation between
the tumor and a critical organ is observed," Dr. Slotman said.

According to Dr. Slotman, this technique could be applied to lung and other
challenging tumors in the upper abdomen that shift as much as several
centimeters with the movement of the patient's diaphragm.  Normally,
radiation oncologists must compensate for motion by irradiating a large margin
of healthy tissue around the tumor.  This limits the amount of radiation
that can be delivered to the tumor, making it more difficult to eradicate the
cancer. 

In four-dimensional CT scanning, information about a patient's breathing
pattern is captured during the acquisition of CT images .  A computer
system sorts, or "bins," the images based on the phase of the respiratory
cycle during which they were acquired.  Using these grouped images, the
system can reconstruct volumetric CT images that correspond with a specific
phase of the patient's respiratory cycle.  Physicians can then select the
best moment during the breathing cycle to activate a narrowed and more finely
focused radiation beam.  Since smaller amounts of normal tissue are
irradiated, higher doses to the tumor, aiming at higher cure rates, can be
delivered.

Combining PET and CT Images for Treatment Planning
Dr. Chao discussed the power of combining positron emission tomography
(PET) and CT images during treatment planning, to generate more precise
radiation delivery strategies that are carefully customized to address the
specific geometric and metabolic characteristics of every tumor.  "PET
can provide the pathological and physiological characteristics of tumors,
while CT can only show the anatomical presence of a mass," he said.  "But
a mass may or may not be a tumor.  Even if it is a tumor, it may or may
not be aggressive enough to warrant aggressive therapy." 

CT scans provide anatomical data, while PET images highlight the most
metabolically active parts of a tumor.  By using both, doctors can see
the extent of the tumor more clearly, and determine which areas are growing
the fastest.  This enables them to develop more precise treatment
plans.  According to Dr. Chao, using PET image data in addition to CT
images for treatment planning has repeatedly caused him to make different
treatment prescription decisions than he would have made using CT image data
alone.

"Having the PET images helps with diagnosis, and it helps with treatment
planning," he pointed out.  "In diagnosis, we know immediately where the
tumors are, and how big, and how active.  Later, PET images help us
design the treatment more appropriately."

Treating Pediatric Cancer With IMRT
The long-term quality of life for children who survive childhood cancer
can be significantly improved thanks to image-guided modalities like IMRT,
according to Dr. Wolden, who said IMRT has made a difference to children who
were treated for cancer at Memorial Sloan Kettering Cancer Center. 

"Many pediatric cancers require radiation therapy, but this can cause
significant long-term complications," she said. 

For example, a pediatric brain tumor called medulloblastoma can be treated
with radiation.  Using IMRT can prevent severe hearing loss, which has
been a common complication of treatment.  With IMRT, the dose to the
inner ear is minimized, and hearing can be preserved in most patients, she
said.

Dr. Wolden also pointed out that IMRT treatments for tumors growing near
critical bones could minimize damage so that children can grow normally. 
"Many who were treated for cancer in the past ended up with some cosmetic
deformity, a shortened limb or some other kind of disfigurement, because
radiation stopped the bone growth.  With IMRT, we can often keep the dose
to the bone within acceptable limits and prevent this."

In some cases, she added, IMRT can preserve vision or hormone function, or can
spare normal organs like the heart, lung, and kidneys.  "Pediatric tumors
occur all over the body," she said.  "With IMRT, all of these important
normal tissues can be preserved."

"It's exciting, to see what advances in imaging are making possible in the
field of radiation oncology," said Richard M. Levy, President and CEO of
Varian Medical Systems, Inc., sponsor of the symposium at which these
presentations were made.  "At Varian, we are committed to helping
clinicians learn about the latest techniques in image-guided radiation
therapy.  It's going to help a lot of future cancer patients, and
weíre proud to be part of the solution."

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