http://english.pravda.ru/news/science/22-08-2006/84027-proton-0
08/22/2006 12:49
Soon cancer to be treated with protons
Cancer is a class of diseases or disorders characterized by uncontrolled
division of cells and the ability of these cells to invade other tissues,
either by direct growth into adjacent tissue through invasion or by
implantation into distant sites by metastasis. Metastasis is defined as the
stage in which cancer cells are transported through the bloodstream or
lymphatic system. Cancer may affect people at all ages, but risk tends to
increase with age, due to the fact that DNA damage becomes more apparent in
aging DNA. It is one of the leading causes of death in developed countries.
Francis Maloy lay on his back on a narrow, metallic table, waiting for a
giant machine to bombard the tumor in his chest with proton beams.
"The last time I heard about protons I was in college taking physics,"
said Maloy, a 68-year-old retired Army colonel from Stuart, Florida, just
before the procedure.
Maloy, who has advanced lung cancer, is one of the first patients being
treated at the University of Texas M.D. Anderson Cancer Center's new US$125
million (?97 million) Proton Therapy Center.
It is the largest of the nation's four centers that treat cancer by
targeting proton beams narrowly on the tumor itself, sparing the healthy tissue
that with typical X-ray radiation would be blasted along with the cancer cells.
While newer forms of traditional radiation, with the help of computers,
also allow doctors to precisely target a tumor, proton therapy allows higher
levels of radiation. For a patient like Maloy, it could be his best hope at
this stage of his cancer.
Dr. James Cox, chief of radiation oncology at M.D. Anderson, was not
always a believer in the technology. But he said studies have shown proton
therapy allows a higher level of radiation on the tumor, with less damage to
healthy tissue and fewer side effects, such as loss of appetite, diarrhea and
headaches. "That was the breakthrough, what changed my mind," he said.
"Anytime you have cancer in any location where it requires a high dose
for control and it's close to sensitive normal structures (such as the eye, the
skull, the spinal cord) that's an indication for proton therapy," Cox said. It
also is useful for treating cancer in children, who are more sensitive than
adults to the side effects of radiation.
Doctors at M.D. Anderson are using proton beam treatments mostly on
patients whose cancers are so early in development that a cure is possible. But
it is also being used on people like Maloy, who have relatively advanced
cancers, Cox said.
Proton therapy has been around since the mid-1950s, but was done mostly
at research facilities, according to the National Association for Proton
Therapy. The world's first hospital-based facility opened in 1990 at Loma Linda
University Medical Center in California.
M.D. Anderson's new center is the largest, covering 94,000 square feet
(8,700 square meters) that include five treatment rooms. The massive machinery
used to produce the proton beams looks like something from a science-fiction
spaceship. Behind three of the treatment rooms are steel barrels three stories
high and weighing 190 U.S. tons (170 metric tons). They house bending magnets,
electrical wires and monitors that work with a tubular device called an
injector and a compact particle accelerator to create and energize the protons
and send them into a patient's tumor, Associated Press Writer Juan A. Lozano
says.
But proton therapy, which is covered by Medicare and most insurance
companies, is about three times more expensive than traditional radiation, in
part because of the cost of the facilities, Cox said.
Some doctors worry that the benefits to a few cancers do not outweigh the
enormous costs, especially when recent advances in traditional radiation make
it safer to use.
Dr. Eric Horwitz, clinical director of the Department of Radiation
Oncology at Fox Chase Cancer Center in Philadelphia, said proton therapy has an
advantage in treating relatively rare cancers such as those in children or of
the spinal cord.
More study is needed to find out if it is more effective for common
cancers, such as prostate and lung, than the newer, cheaper forms of
traditional radiation, he said.
A study in September in the Journal of the American Medical Association
concluded that men who were treated for prostate cancer with higher doses of
radiation, in part through proton therapy, were less likely to have cancer
return than men who got traditional X-ray radiation treatment. The study,
funded by a National Cancer Institute grant, was conducted by doctors who work
at two of the country's other proton therapy centers.
An accompanying editorial to the study by Drs. Theodore DeWeese and Danny
Song with Johns Hopkins University School of Medicine in Baltimore questioned
whether higher doses of radiation are the best way to improve outcomes.
"As such, this study has not answered the important question of whether
patients should accept the modest but real incremental risk of higher radiation
doses for the uncertain ultimate benefit derived," DeWeese and Song wrote.
But proponents like Dr. Nancy Mendenhall, medical director of the new
Florida Proton Therapy Institute in Jacksonville , says that reducing
radiation's side effects could translate into lower health care costs in the
long run, the AP reports.
"I think it will be a part of mainstream radiation oncology if we fully
embrace its advantages," she said.
As for lung cancer patient Maloy, he is getting proton therapy five days
a week for about two months, plus weekly chemotherapy.
"I feel nothing in there, except it's uncomfortable laying on their
machine," he said. "You don't know anything is happening. It's magical."
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