Chemotherapy uses powerful drugs to kill cancer cells. For children with medulloblastoma, chemotherapy is used to reduce the risk of tumor cells spreading through the spinal fluid. For adults, this benefit is not quite as clear since their tumors tend to regrow in the cerebellum. Because different drugs are effective during different phases of a cell’s life cycle, a combination of drug may be given. The combination increases the likelihood of more tumor cells being destroyed.
Chemotherapy is now a standard part of treatment for children with medulloblastoma. Most children are treated in clinical trials — organized studies that are helping determine which treatments are most effective. Clinical trials also offer a formal way to test new therapies against existing therapies to learn which is better.
In children at average-risk of recurrence, current studies are exploring the use of chemotherapy as a way to reduce the total amount of craniospinal radiation. There are several treatment plans in use, but most focus on a combination of vincristine, cisplatin, lomustine, and/or cyclophosphamide.
For children at high-risk, the drugs vincristine, cisplatin, and cyclophosphamide tend to be the main focus, but others are being tested in clinical trials. Researchers are also looking at the use of chemotherapy as a radiation sensitizer, and at “post-radiation” high-dose chemotherapy accompanied by a stem cell transplant.
For infants under the age of 3, chemotherapy is used to delay or even eliminate radiation therapy. Cyclophosphamide, vincristine, cisplatin, etoposide, carmustine, procarbazine, cytarabine, and/or hydroxyurea may be found in these treatment plans. New drugs are under consideration, but their effectiveness is generally determined in older children prior to use in infants. Some treatment plans use higher doses of chemotherapy, supported by peripheral stem cell rescue, for infants. There is also interest in instilling chemotherapy directly into the cerebrospinal fluid (either “intrathecally” — into the lumbar spine by spinal taps, or “intraventricularly”—
into the ventricular fluids of the brain via an Ommaya reservoir). This is being done in attempts to deliver high doses of therapy to the coating regions of the brain and reduce disease relapse in these areas. In addition, studies are underway evaluating the efficacy and safety of utilizing local radiation therapy (radiation therapy only to the primary tumor site) after chemotherapy in infants whose initial disease was limited to the posterior fossa.
In adults, the usefulness of chemotherapy is less clear. Although large scale studies have not been done, some smaller studies indicate adult tumors may likewise respond to some of the above combinations. But adults seem less able to withstand potential side effects, especially those of the lomustine and cisplatin used in some treatment plans. Studies are exploring the use of cyclophosphamide, ifosfamide, etoposide, or carboplatin in adults, and other studies are exploring pre-radiation chemotherapy plans as alternatives.
Research continues into defining the best use of chemotherapy in average-risk patients; the best tolerated drugs in adults: and new drugs targeted to specific genetic changes found in medulloblastomas. Your doctor will outline a treatment plan based on current studies, the patient’s age, the amount of remaining tumor, and the risk of further disease.