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In a study on rats, researchers use magnets, ultrasound and tiny particles to deliver chemotherapy drugs to precise locations. Clinical trials on humans are at least four to five years away.

Patients with brain tumors don't have many good options — surgery and radiation can damage crucial parts of the brain, and chemotherapy drugs don't easily cross the blood-brain barrier. A new procedure using magnets, ultrasound and minuscule drug-coated particles may be an effective solution, according to a study on rats published in Tuesday's edition of the journal Proceedings of the National Academy of Sciences.

The researchers, led by Dr. Kuo-Chen Wei of Chang Gung University in Taiwan, injected tiny magnetic beads called nanoparticles, coated with a chemotherapy drug, into the rats' tails. They used ultrasound to open up a small region of the blood-brain barrier and a magnetic field to attract the particles to a precise location in the brain.

When they applied the treatment to rats with brain tumors, the tumor growth was slowed and the rats lived two-thirds longer than untreated rats.

"The technology's not very difficult," Wei said, "but the idea is novel."

Clinical trials in human beings are at least four to five years away, he added.

Brain tumors are difficult to treat with traditional drug delivery methods because the brain is insulated from circulating blood. Focused ultrasound — similar to, but much stronger than, the ultrasound technique used on pregnant women — temporarily disrupts the barrier, allowing drugs to enter.

Once the drugs get into the brain, they should ideally be delivered to a precise location to cut down on the damage to healthy tissue. This report is the first in which magnetic targeting was combined with ultrasound to attract the nanoparticles — and their drug passengers — to a specific part of the brain.

"The method has significant clinical potential," said Dr. Kullervo Hynynen of the University of Toronto Medical School, who conducts similar research but was not involved in the new study.

Wei and his team are working to improve the treatment so they can apply it to human patients. He said they needed to try additional chemotherapy drugs and nanoparticle types, as well as improve the ultrasound and magnetic-targeting technology.

Still, some scientists worry that opening the blood-brain barrier to allow powerful chemicals into the brain is too dangerous.

"The potential for toxicity in normal brain regions could cause all kinds of problems," said Allan David, a drug delivery researcher at the University of Michigan. "I think it's an interesting study, but it's still far from clinical studies."

Some of the danger of opening the blood-brain barrier may be avoided by combining Wei's approach with a type of drug that is activated only upon reaching the tumor, David said, so that healthy brain tissue is left unharmed.

Source: Los Angeles Times