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Duke Cardiologists Improve Outcomes of Angioplasty with Small Doses of Radiation

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Duke Health News 919-660-1306

DURHAM, N.C. - While the widespread use of tiny flexible
tubes called stents has greatly improved the outcomes for heart
patients receiving angioplasty, cardiologists still find that
the arteries of almost one-quarter of these patients will
become clogged again in a process known as restenosis.

Recent clinical trials - some conducted at Duke University
Medical Center - have demonstrated that small measured doses of
radiation delivered immediately after an angioplasty procedure
reopens a clogged stent and can keep the arteries from
re-clogging. This approach has significantly reduced the number
of times patients must have repeat procedures to keep their
arteries open, the researchers say.

It is estimated that more than 100,000 patients in the
United States need treatment for restenosis annually.
Currently, Duke is one of the few institutions to offer two new
and different approaches to radiation treatment - one is based
on beta radiation, the other based on gamma radiation. Both
systems were approved for use in November by the Food and Drug
Administration (FDA). Duke performed its first procedures since
approval this month.

"More than 75 percent of the approximately 1 million
Americans who receive angioplasty procedures each year also
receive a stent, and of those patients, about 25 percent will
experience restenosis," said Duke cardiologist Dr. Michael
Sketch Jr. "Before the advent of radiation treatments, there
was nothing out there proven effective for restenosis.

"Radiation has the same potential for making a huge impact
on the treatment of restenosis as stents have made on the
treatment of new blockages," said Sketch, who serves as
director of the cardiac catheterization laboratories at
Duke.

In an angioplasty procedure, a tiny balloon is threaded
through an artery to the site of blockage, where it is
inflated, pushing the atherosclerotic plaque to the side.

In more and more cases, cardiologists will then deploy a
stent, a tiny wire mesh tube designed to keep an newly cleared
artery open.

However, while this process opens a larger channel for blood
to flow through, it also stimulates the abnormal growth of the
cells lining the artery, which can then re-block the treated
artery. Past clinical trials have shown that when delivered at
the same time the artery is re-opened, the radiation interferes
with the endothelial cells proliferative response.

"When the balloon is inflated, it causes damage to the
lining of the artery," explained Dr. Tim Shafman, a radiation
oncologist who works with Duke cardiologists. "The body
responds by growing new endothelial cells at the site. While
the exact reasons why radiation works is unclear, we do know
that it seems to inhibit the growth of these cells."

The researchers add that radiation also is used in other
medical conditions to control the abnormal growth of
tissue.

Beta radiation has been used for decades to treat keloids,
large growths of scar tissue on the skin caused by
proliferation of normal tissue in response to an injury. When
treated with a small amount of radiation after removal, the
keloids seldom returns. Radiation also is being used at Duke to
prevent the abnormal proliferation of bone cells after total
hip replacement.

The recently completed START (STents And Radiation Therapy)
trial of the Beta-Cath system demonstrated that the incidence
of restenosis was 36 percent to 66 percent lower in patients
treated with the system when compared to placebo. The START
trial was conducted at 50 sites, including Duke, under the
direction of Brigham and Women's Hospital in Boston. The
Beta-Cath system was developed by Novoste Corp., Norcross,
Ga.

The Beta-Cath system uses strontium-90 as its source of beta
radiation, while the Checkmate system uses iridium-192 as its
source of gamma radiation. The Checkmate system, developed by
Cordis Corp., of Miami, was shown in the recently completed
Gamma I trial to have 41 percent fewer instances of restenosis
when compared to placebo. The Gamma I trial was conducted at 12
hospitals, including Duke, under the direction of Washington
Hospital Center in Washington. To date, the two types of
systems have not been compared to each other in a clinical
trial.

"In both systems, the radiation is caused by the slow
disintegration of the source elements, and from the patients'
perspective, it doesn't really matter which source is used,"
Shafman said.

The radiation is applied after the balloon angioplasty
device is withdrawn from the patient. A slender hollow tube is
inserted through the artery to the site of treatment. Once at
the site, small seeds of radiation are sent through the tube to
the area to be treated. At no time does the solution leave the
device and come into contact with tissue, Sketch said, and the
radiation only travels a short distance from its source.

For a beta procedure, the radiation remains in the patient
for about three to five minutes, while the gamma approach
requires about 20 minutes. When gamma radiation is used,
physicians and technicians must remain behind a lead shield
during treatment.

There are many factors that cardiologists use when
determining which approach to use, one of the most important
being the size of the lesion, or area of treatment. The
Beta-Cath system is approved for lesions up to 20 millimeters
long, while Checkmate is approval for lesions up to 45
millimeters.

"The important thing for heart patients at Duke is that we
have at our disposal the latest techniques and technologies for
treating heart disease," Sketch said. "We should be able to
make a great impact in the outcome of our patients. With both
systems here at Duke, we can evaluate which one is the best for
each individual patient."

Cutline:

Dr. Michael Sketch Jr., standing, conferring with Dr. Tim
Shafman in the control room in one of Duke University Medical
Center's cardiac catheterization labs.

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