At
the Midwest Proton Radiation Institute,
located at the IU Cyclotron Facility
in Bloomington, scientists and physicians are using proton radiation to give
the gift of sight. They are experimenting with a treatment for age-related macular
degeneration, a disease which can cause irreversible vision loss.
Millions of people are affected
by AMD, particularly those between the ages of sixty-five and eighty-five. About
28 percent of people between seventy-five and eighty-five have the disease,
and about 10 to 20 percent of those exhibit the “wet” form of the
disease that has been under study at the MPRI.
Wet AMD is characterized
by the growth of new blood vessels at the back of the eye, where they don’t
belong. Very small capillaries form a membrane under the retina, leading to
blindness.
“We don’t know
what causes it, and there’s no standard treatment,” says Susan Klein,
AMD project director at the MPRI. “But lots of people suffer from it.”
These factors—the widespread
nature of the disease, its mysterious causes, and the lack of an effective remedy—made
AMD a good first target disease for proton radiation therapy, according to Klein.
With doctors from the IU School of Medicine’s Department of Ophthalmology
and the School of Optometry, the MPRI
launched a Phase III clinical trial in 1997 to determine the effectiveness
of radiation in controlling AMD.
“We knew that with
radiation, we could stop blood vessel growth,” Klein says. “The question
is, is it stopped permanently, or do we have to keep re-treating?”
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| Susan Klein, project director for the age-related macular degeneration research project at Indiana University's Midwest Proton Radiation Institute, adjusts the head brace at the end of a proton radiation beam line. The head must be kept steady to within 1 millimeter. Courtesy photo. |
A total of thirty-nine patients
participated in the recently completed trial. The therapy—a specific dose
of a proton radiation beam—was delivered in a room adjacent to the cyclotron.
As a patient sits in what looks like a dentist’s chair, a traction-like
apparatus holds his or her head still while a tiny cylinder of radiation passes
through the white part of the eye and stops at the back of the membrane. Treatments
last only one minute; patients received a total of two treatments.
Although they looked down
the “snout” (as it’s called in medical physics) of a radiation
beam line, the AMD trial patients were not anxious, Klein says. “They were
just phenomenal people,” she says. “They were very excited about the
treatment and about participating in a study that could make a real difference.”
Just how much of a difference
the proton therapy may make isn’t known yet. “The unfortunate thing
about clinical research is that you don’t really know answers until you’ve
followed the patients for some time,” Klein admits. “We’re continuing
to analyze the data. The results should be available in about 12 months.”
AMD is not the only ailment
under study at the MPRI. Klein and colleagues are also investigating the possible
use of proton radiation
to treat serious angina, a disease marked by intense spasms of chest pain.
One of the most novel treatments for angina involves opening up a person’s
chest and using a laser to drill fifteen to thirty channels in the left ventricle
of the heart. The trauma causes new blood vessels to grow, and the increased
blood flow helps angina patients feel better.
With proton radiation, scientists
and doctors can go deep into the body’s tissues without opening up the
chest cavity. “We know we can cause new vessels to grow with radiation,”
Klein says. “The idea is to make channels in the heart and relieve angina
in the same way the more invasive therapy does.” The procedure is being
tested on animal hearts before moving forward with clinical trials.
The future of proton radiation
therapy at the MPRI looks bright, according to Klein. The proton beam’s
precision and its capability to reach very small structures inside the body
make it a powerful tool for medical research and therapy.
“We can always target something better with protons than with photons or electrons,” Klein says. “Protons are always better.”— L.B.