Even with aggressive treatment consisting of surgery, radiation therapy, and intavenous chemotherapy, less than half of patients live more than one year. Surgery and radiation therapy have probably reached maximal effectiveness. Chemotherapy still has the potential to improve survival but has had only limited success for several reasons. Also, even when the drug does get into the brain, it remains active in the body for only a few hours and does not have enought time to destroy the tumor. In addition, intravenous chemotherapy often produces severe toxicity and so cannot be given in high enought doses to be effective in the brain.
Intratumoral chemotherapy has several advantages over intravenous chemotherapy.
Large amounts of the drug can be concentrated in the brain tumor because the blood-brain barrier is bypassed. These large concentrations of the chemotherapy drug in the tumor are achieved by giving very small doses of the medicine, thus little drug gets into the systemic circulation to cause toxicity. In addition, new type of drugs that could not be given by intavenous injections and so have never before been used in the treatment of brain tumors can now be injected directly into tumors. Finally, it is possible to give intravenous chemotherapy by continuous infusion or by sustained release and maintain high drug concentrations in the tumor for indefinitely long periods of time so that the drugs have adequate time to work. This method requires a large operation during which the brain is opened and the wafers are placed inside the tumor.