Chemotherapy uses chemicals (drugs) that have a toxic effect on tumor cells as they divide. The drugs interfere with the normal functioning of the rapidly dividing cells of the tumor to prevent tumor growth. Chemotherapy is usually a secondary therapy. It is usually not used for the treatment of noncancerous brain tumors.
Chemotherapy is usually taken orally or by injection, and may be given alone or in combination with other treatments. Chemotherapy is given in cycles, which consist of “on” and “off” phases – days of treatment followed by periods of time between treatments. Cycles vary depending on the drug or drugs used.
Another way to delivery chemotherapy to the brain is through polymer wafer implants. With this method, biodegradable wafers are saturated with a chemotherapy drug, BCNU, and placed directly inside the tumor cavity at the time of surgery. The wafers are left there to dissolve over a short period of time. In this way, a concentrated dose of BCNU (approximately 100 times higher than that tolerated through IV) can be delivered directly to the tumor site without increasing side effects.
Chemotherapy can decrease the chance of a brain tumor spreading outside the nervous system. Chemotherapy has been particularly effective in treating children with brain tumors that have spread outside the brain to the bone or bone marrow. The use of chemotherapy also helps delay or replace the use of radiation treatment in children, which can be harmful to the developing brain.