Delivering drugs directly to brain tumors.

Malignant brain tumors are extremely tough to treat. The blood-brain barrier often prevents anticancer agents in the bloodstream from entering the brain to attack tumor cells. Physicians therefore want to deliver cancer-killing drugs directly to brain tumor cells.

Henry Brem, a neurosurgeon at the Johns Hopkins Medical Institutions in Baltimore, is developing small polymer disks containing anticancer drugs for implantation at tumor sites. After removing a tumor, a surgeon can line the cavity with dime-size disks that slowly release tumor toxins directly to cancerous tissue.

This method increases the drug dose at the cancer site while minimizing side effects on the patient's system.

In the laboratory, Brem's team is testing various slow-release polymers, including two polyanhydrides, in conjunction with several FDA-approved anticancer drugs. In the first clinical trial, which included 222 patients at 27 medical centers, polymers containing the anticancer agent carmustine, or BCNU, "significantly prolonged patient survival," says Brem.

"In marked contrast to the many toxic effects commonly experienced by patients treated with systemic or intra-arterial BCNU therapy, no significant adverse effects were associated with these implants," he adds.

Researchers are now planning further clinical studies of polymer implants, using other drugs and stronger doses of BCNU.