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A new implantable, biodegradable, polymer disk that delivers extremely high doses of chemotherapy to brain tumors offers hope for patients suffering from brain cancer, researchers said Thursday.

A group of researchers from the United States and Canada found that patients who received drugs via the disks lived on average two months longer than patients who received placebo disks. The implantable disk represents an entirely new method for delivering drugs to the brain."It is a new approach to treating brain tumors," said Dr. Henry Brem of the Department of Neurological Surgery and Oncology at the Johns Hopkins University and lead author of the study. "And, it prolonged survival as well as improved the patients' quality of life."

Although survival gains were modest, the polymer disks could be used to deliver a wide variety of drugs to the brain. The method could one day be used to treat other types of tumors.

"What is so important is that we have a new approach to treating brain cancer by wrapping the drug into a polymer," Brem said. "It exposes the tumor to phenomenal doses of the drug and shields the body from toxic effects."

Brain cancer ordinarily has a terrible prognosis. The tumor can be removed, but it often returns. Complicating matters, any drug that is used to treat the cancer must pass through the "blood-brain" barrier - a physical barrier that protects the brain from exposure to blood-born pathogens.

Because chemotherapy drugs are toxic to so many normal cells, it is difficult to get enough drug across the blood-brain barrier to kill the brain tumor.

However, with the drug-laced polymer disks, the surgeons can remove the tumor and line the resulting cavity with the polymer disks. The disks release drugs and slowly degrade over two to three weeks. Previous animal studies indicate that very high concentrations of the drug can be delivered to the brain using this method.

Brem and his colleagues studied 222 patient with brain cancer relapses. Half of the patients were treated with polymer disks containing the common chemotherapy drug carmustine and the other half were treated with placebo disks that contained no drug.

As the researchers report in the current issue of the British journal The Lancet, patients who had disks with the drug survived on average 31 weeks while patients with the placebo disks had an average survival of 23 weeks.

More importantly, the patients who received the drug-drenched disks did not suffer illnesses associated with systemic chemotherapy.

"We were able to deliver extremely high doses without any toxicities," Brem said.

Although the increase in survival may seem inconsequential, Brem said noted that these patients had failed to respond to all other types of treatment. "Typically, these patients are very difficult to treat," Brem said.

Using the polymer disks, Brem and his colleagues are considering exposing brain tumors to drugs that ordinarily cannot pass the blood brain barrier like taxol.

"In that case, the blood brain barrier works to our advantage because it keeps taxol in the brain and doesn't let it enter the blood stream," Brem said.

Brem hopes to test this technology on patients who are first diagnosed with brain cancer. And, other physicians intend to use the delivery method to treat disease like epilepsy.