Chemotherapy:

Chemotherapy involves the use of drugs to kill or alter cancer cells. Chemotherapy is not an effective initial treatment for low-grade brain tumors, mostly because standard drugs cannot pass through the blood-brain barrier, the functional system that protects the brain by preventing certain molecules from reaching the central nervous system. In addition, not all types of brain tumors respond to chemotherapy. In general, chemotherapy for brain tumors is usually administered following surgery or radiation therapy.

The type of drug determines how it is administered. "Systemic delivery" drugs, which pass to the brain from the bloodstream, may be given by mouth, injected into a vein through an IV, or injected into an artery or a muscle. "Local delivery" drugs are placed within or around the brain tumor.

Scientists are working on several approaches to overcome the blood-brain barrier. Newer delivery methods include:

• Interstitial chemotherapy uses disc-shaped polymer wafers (known as Gliadel wafers) soaked with carmustine, the standard chemotherapeutic drug for brain cancer. The surgeon implants the wafer directly into the surgical cavity after a tumor is removed.
• Intrathecal chemotherapy delivers chemotherapeutic drugs directly into the spinal fluid.
• Intra-arterial chemotherapy delivers high-dose chemotherapy into arteries in the brain using tiny catheters.
• Convection-enhanced delivery (CED) involves placing catheters into the brain tumor or nearby brain tissue to deliver slowly and continuously a cancer drug over several days.

Chemotherapy Drugs and Regimens

Many different drugs, and drug combinations, are used for chemotherapy. Standard ones include:

Temozolomide (Temodar). Temozolomide, the first new drug approved for brain tumors in several decades, is taken by mouth as a pill. Temozolomide was first approved in 1999 for adult patients with anaplastic astrocytoma that did not respond to other treatments. In 2005, it was approved for use during and after radiation therapy for patients newly diagnosed with glioblastoma multiforme. The current first-line treatment for patients with glioblastoma is combined radiotherapy and temozolomide, followed by monthly doses of temozolomide after radiation treatment ends. The drug may work best for patients with a specific genotype. Temozolomideâ ' s side effects are relatively minor, but may include constipation, nausea and vomiting, fatigue, and headache.

Carmustine (BCNU, BiCNU). Carmustine is used to treat many types of brain tumors, including glioblastoma, medulloblastoma, and astrocytoma. Carmustine is usually administered into the vein by IV. It can also be delivered through a wafer implant (Gliadel), which is surgically placed into the brain cavity after tumor removal. If carmustine is administered intravenously, side effects may include nausea and vomiting, fatigue, respiratory problems, and lung scarring (pulmonary fibrosis). Intravenous carmustine may cause bone marrow impairment, which results in decreased production of blood cells (a condition called myelosuppression). If carmustine is delivered through a wafer, side effects may include seizures, brain swelling, and infection within the brain cavity.

PCV Drug Regimen. PCV is an abbreviation for a chemotherapy regimen that combines procarbazine (Matulane), lomustine (CCNU), and vincristine (Oncovin). PCV is commonly used to treat oligodendrogliomas and mixed oligoastrocytomas. The drugs may also be used alone or in other combinations. Procarbazine and lomustine are taken by mouth. Vincristine is given by either injection or IV. These drugs can cause significant side effects, including a drop in blood cell counts, nausea and vomiting, constipation, fatigue, and mouth sores. Procarbazine can cause high blood pressure when taken with foods high in tyramine. Patients should avoid foods such as beer, red wine, cheese, chocolate, processed meat, yogurt, and certain fruits and vegetables.

Platinum-Based Drugs. Cisplatin (Platinol) and carboplatin (Paraplatin) are standard cancer drugs that are sometimes used to treat glioma, medulloblastoma, and other types of brain tumors. These drugs are delivered by IV. In addition to nausea and vomiting, carboplatin can cause hair loss, and cisplatin can cause muscle weakness.

Other Chemotherapy Drugs. Researchers are investigating whether drugs used to treat other types of cancer may have benefits for brain tumors. These drugs include:

• Tamoxifen (Nolvadex) and paclitaxel (Taxol), which are used to treat breast cancer
• Topotecan (Hycamtin), which is used to treat ovarian and lung cancers
• Vorinostat (Zolinza), which is approved for treatment of cutaneous T-cell lymphoma

Irinotecan (Campath) is another cancer drug that is being studied in combination treatment.

Investigational Biologic Drugs (Targeted Therapy)

Traditional chemotherapy drugs can be effective, but because they do not distinguish between healthy and cancerous cells their generalized toxicity can cause severe side effects. Targeted therapies work on a molecular level by blocking specific mechanisms associated with cancer cell growth and division. Because they selectively target cancerous cells, they may induce less severe side effects. In addition, these drugs hold the promise of creating options for more individualized cancer treatment based on a patient's genotypes. To date, none of these drugs have been approved by the FDA for brain tumor treatment, but they are being actively investigated in clinical trials.

Promising targeted therapies for brain tumors include:

• Anti-angiogenesis drugs block molecules involved with the growth of blood vessels that feed the tumor (a process called "angiogenesis," which is particularly important in the growth of glioblastomas.) These drugs starve tumors of vital nutrients and oxygen. Bevacizumab (Avastin) is being studied in combination with irinotecan for treatment of recurrent malignant gliomas. Bevacizumab, which targets vascular endothelial growth factor (VEGF), a specific angiogenesis growth factor, is the most studied of these drugs. Cediranib (Recentin, AZD2171) is another VEGF inhibitor being investigated for glioblastoma treatment.
• Tyrosine kinase inhibitor drugs block proteins involved in tumor cell growth and production. Drugs that specifically target epidermal growth factor receptors (EGFR) are a type of tyrosine kinase inhibitor of special interest in brain tumor research. These drugs include erlotinib (Tarceva), imatinib (Gleevac), and gefitinib (Iressa).
• Farnesyl protein transferase inhibitors, such as tipifarnib (Zarnestra) and lonafarnib (Sarasar), are drugs that target a protein involved in the functioning of the cancer-causing Ras protein. Lonafarnib is being studied in combination with temozolomide, and tipifarnib in combination with radiation therapy.
• MTOR inhibitors target other enzymes involved in cell growth and replication. Everolimus (RAD-001) is being studied for glioblastoma multiforme and astrocytoma. Everolimus is related to rapamycin (Siroliumus) and tacrolimus (Prograf), which are also being investigated for brain tumor treatment. These drugs are commonly used to suppress the immune system to prevent rejection after organ transplantation.