Medical Health Encyclopedia

Because chemotherapeutic drugs may also affect normal cells, side effects are common. To help offset these effects, chemotherapy is given intermittently over a scheduled period that allows normal cells to recover between treatments. Side effects include nausea, vomiting, fatigue, infection, bleeding, and hair loss. In addition, the agents used to treat symptoms (anti-seizure drugs, antidepressants, and corticosteroids) may interfere with standard chemotherapeutic agents. Specific drugs may have different complications; for example, vincristine can cause nerve injury and cisplatin may result in hearing loss. Procarbazine requires dietary restrictions. Side effects are almost always temporary and may be managed with other medications.

Approaches to Enhance Drug Access to the Tumor

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To make chemotherapy more effective, scientists are working on a number of approaches to overcome an obstacle unique to brain cancer: the blood-brain barrier, a functional barrier that protects the brain and prevents certain molecules from passing through.

• Certain drugs, such as mannitol or agents called receptor-mediated permeabilizers, may open the barrier without worsening neurological deficits.
• Interstitial chemotherapy uses disc-shaped wafers (known as Gliadel wafers) soaked with carmustine, the standard chemotherapeutic drug for brain cancer. The doctor places the wafer directly into the surgical cavity after a tumor is removed. Studies suggest that this approach can improve survival in some patients. The procedure does not appear to increase the risks of side effects over those of the surgery itself.
• Intrathecal infusion delivers chemotherapeutic drugs directly into the spinal fluid.
• Intraarterial delivery administers high-dose chemotherapy into arteries in the brain using tiny catheters. In a 2000 study, this approach was used within two weeks of radiotherapy in patients with high-grade astrocytomas, and the survival rates for glioblastoma multiforme tripled (20 months) compared to those who had chemotherapy and radiation at the same time.
• Enclosing highly potent anti-cancer drugs, such as anthracyclines, in protective microspheres (called liposomes) may allow the drugs time to enter tumors without unduly increasing the risk for severe toxicity. Such agents are not ordinarily used for brain cancers because of high toxicity and poor penetration of brain tumors.
• An investigative technique called electrochemotherapy (ECT) applies high-voltage pulses to deliver drugs across cancerous tissues, including those of the brain.