Because of the impermeability of the blood-brain barrier, which normally protects the brain from drugs and other substances circulating in the blood, many drugs that are used to treat brain cancer cannot reach or attack the tumors. Several clinical trials are now beginning to test new ways of disrupting or opening up the osmotic blood-brain barrier long enough to allow the drugs to enter.
“Smart” drugs might be able to target cancerous cells with less toxic effects compared with traditional chemotherapy. Catheters are being tested in an approach called convection-enhanced delivery, and wafers containing chemotherapeutic agents have been approved.
It is hoped that these new methods of delivering chemotherapy might also be used to treat Alzheimer’s disease, Parkinson’s disease, and stroke. However, these advances are not without pitfalls, because potentially lethal agents may also cross the barrier in the process.