Chemotherapy and Medulloblastoma
What is Chemotherapy?
Chemotherapy, commonly called chemo, is simply any medication that kills cancer cells. Just as “antibiotic” refers to the broad class of drugs used to treat infections, chemotherapy refers to the broad class of drugs used to treat cancer.
Chemotherapy drugs destroy tumor cells by keeping the tumor cells from growing, dividing, and making more cells. Many different types of chemotherapy drugs exist, and each one targets one of the many different aspects of tumor cell division. Patients may receive one chemotherapy drug at a time or a combination of different drugs given at the same time.
Chemotherapy regimens for medulloblastoma usually consist of a defined number of cycles given over a set period of time. There are different types of chemotherapy regimens based on the subtype and stage of medulloblastoma, and the age of the patient.
Chemotherapy treatments may either be conventional or part of a clinical trial.
How is Chemotherapy Administered?
Chemotherapy can be given intravenously (by IV), through an injection into the skin or muscle, orally, or even injected directly into a body cavity (for example, injection into the spinal fluid via a spinal tap/lumbar puncture). Most chemotherapy for medulloblastoma is given by IV.
The majority of patients need a central line or a port to make giving chemotherapy easier and more convenient.
For medulloblastoma, a patient can receive anywhere from 4-9 cycles (months) of chemotherapy. Chemotherapy may also be given while the patient is receiving radiation. Sometimes it’s feasible to administer radiation and chemotherapy at the same time and sometimes it’s not. Your care team will discuss these options with you when working on your treatment plan.
Combination Chemotherapy
For many pediatric cancers, it has been shown that by using combination chemotherapy—two, three, or more drugs together—the child’s survival is improved. This is because several drugs together work better to kill cancer cells than any one drug alone. In addition, if a tumor is resistant to one drug, it may be killed by one of the others given.
A disadvantage of chemotherapy—particularly in treating children with brain tumors—is that it circulates everywhere in the child’s body, and therefore has the potential to kill or damage normally dividing cells. This fact accounts for many of the side effects of chemotherapy.
Chemotherapy Side Effects
Side effects of chemotherapy depend on the individual patient, the type of chemotherapy, and the dose. General side effects include:
- Fatigue
- Low blood counts
- Risk of infection
- Bleeding
- Mouth sores
- Nausea and vomiting
- Hair loss
- Decreased appetite
These side effects tend to go away after treatment is complete.
Challenges of Using Chemotherapy for Children with Brain Cancer
Finding effective chemotherapy for children with brain tumors is more challenging than finding effective chemotherapy for children with other types of cancer. A major challenge with brain tumors is the blood-brain barrier.
Blood vessels in the brain are unique; they are designed to be very selective about what can penetrate them to get into brain cells. They selectively allow nutrients to reach brain cells, but block many unrecognizable, potentially toxic substances including many types of chemotherapy. From an evolutionary standpoint, this makes perfect sense (i.e., protecting our brains from toxins), but when it comes to getting chemotherapy into brain tumors, it is a problem.
Therefore, chemotherapy must be designed to penetrate the blood-brain barrier. The list of drugs that can do this is small, leaving healthcare providers with fewer weapons to use for children with brain tumors.
High-Dose Chemotherapy Followed by Autologous Stem Cell Transplant (HD ASCT)
Some treatment facilities offer high-dose chemotherapy followed by stem cell transplant. Higher doses of chemotherapy are given (higher than a standard round of chemotherapy) with the hopes of destroying more of the tumor or cancer cells. Unfortunately, high-dose chemotherapy can cause temporary negative effects to bone marrow, which can lead to an increased risk of infection. A stem cell transplant is often utilized to help restore the patient's bone marrow, strengthening their immune system.
Research is now being done on the use of stem cell transplants after high doses of chemotherapy for treating medulloblastoma. Early results have shown this regimen may be helpful for some patients. Clinical trials are currently underway to explore this idea further.