What’s new in research and treatment for brain tumors in children?
There is always research going on in the area of brain and spinal cord tumors. Scientists are looking for causes and ways to prevent them, and doctors are working to improve treatments.
Understanding gene changes in tumors
Researchers continue to look for the gene changes that result in brain and spinal cord tumors. The hope is that learning more about these gene changes may lead to better ways to treat these tumors.
For example, researchers have found that medulloblastomas can be divided into 4 main types, based on the different gene changes in the tumor cells. Some of these tumor types have a better outlook than others. Doctors may be able to use this information to help decide which children might need more or less intensive treatment.
More recently, researchers have identified some of the specific gene changes found in each type of medulloblastoma that might help the tumor cells grow. Some of these gene changes can be targeted with new types of drugs, which are now being tested in clinical trials. In the future, doctors may be able to develop other drugs that specifically target these gene changes.
Imaging and surgery techniques
Recent advances have made surgery for brain tumors much safer and more successful. Some of these newer techniques include:
- Functional magnetic resonance imaging (fMRI, described in “How are brain and spinal cord tumors in children diagnosed?”), which can identify the site of important areas of the brain and how close they are to the tumor.
- Image-guided surgery, which lets surgeons create a 3-dimensional image of the tumor and surrounding structures and to control surgical instruments more precisely for safer and more extensive removal of the tumor.
- Fluorescence-guided surgery. For this approach, the patient drinks a special fluorescent dye a few hours before surgery. The dye is taken up mainly by the tumor, which then glows when the surgeon looks at it under special lighting from the operating microscope. This lets the surgeon better separate tumor from normal brain tissue.
- Newer surgical approaches for some types of tumors. For example, a newer approach to treat some tumors near the pituitary (such as some craniopharyngiomas) is to use an endoscope, a thin tube with a tiny video camera lens at the tip. The endoscope is passed through a small hole made in the back of the nose, which allows the surgeon to operate through the nasal passages and limits the potential damage to the brain. A similar technique can be used for some tumors in the ventricles, where a small opening in the skull near the hairline serves as the point of endoscope insertion. The use of this technique is limited by the tumor’s size, shape, and position.
Several newer types of radiation therapy now let doctors deliver radiation more precisely to the tumor, which helps spare normal brain tissue from getting too much radiation. Newer techniques such as stereotactic radiosurgery, 3-dimensional conformal radiation therapy (3D-CRT), intensity modulated radiation therapy (IMRT), and proton beam therapy are described in the section “Radiation therapy.”
The brain is very sensitive to radiation, which can lead to side effects if normal brain tissue receives a large dose, especially if the child is very young. Clinical trials have shown that in some situations, using chemotherapy can let doctors use lower doses of radiation therapy without lowering the chance that treatment will be effective. Doctors are now trying to determine if even lower doses of radiation can be used and still yield the same results.
New approaches may help make chemotherapy more useful against brain and spinal cord tumors.
In some children and infants with brain tumors, chemotherapy is given right after surgery to either delay radiation therapy (particularly in infants) or to decrease the radiation dose needed to treat the tumor. This is known as adjuvant chemotherapy. Some studies are looking at whether giving prolonged chemotherapy may help avoid the need for radiation therapy at all in certain cases.
High-dose chemotherapy and stem cell transplant
One of the main factors that limits the doses of chemotherapy that can be given safely is its effects on the bone marrow, where new blood cells are normally made. A stem cell transplant allows higher doses of chemotherapy to be given than would normally be possible. First, blood stem cells are removed from either the child’s blood or the bone marrow and are stored in a deep freeze. The child is then treated with very high doses of chemotherapy. The blood stem cells are then thawed and infused back into the body, where they settle in the bone marrow and start making new blood cells.
Although some children have had good responses to this very intensive treatment, it can have serious side effects, and it is not yet known if it is effective enough to become standard. For now, most doctors consider this treatment experimental for brain tumors. Clinical trials are being done to determine how useful it is.
Improving chemotherapy drugs
Many chemotherapy drugs are limited in their effectiveness because the tightly controlled openings in the brain capillaries, sometimes referred to as the blood-brain barrier, prevents them from getting from the bloodstream to some parts of the brain tumor. Researchers are now trying to modify some of these drugs by coating them with tiny layers of fat (liposomes) or attaching them to molecules that normally cross the blood-brain barrier, to help them work better. This is an area of active research.
Getting chemotherapy directly to tumors
Some new approaches may help doctors get chemotherapy directly to tumors.
In adults, doctors sometimes place special wafers containing chemotherapy directly at the site of a brain tumor during surgery. The wafers dissolve and give off doses of chemotherapy over several weeks, keeping a high concentration of the drug at that spot while sparing the rest of the body from the possible side effects. Studies are now under way to see if this will work in children as well.
For a newer method called convection enhanced delivery, small tubes are placed into the tumor in the brain through a small hole in the skull during surgery. The tubing extends through the scalp and is connected to an infusion pump, through which chemo drugs can be given. This may be done for hours or days and may be repeated more than once, depending on the drug used. This is still an investigational method, and studies are continuing.
Other new treatment strategies
Researchers are also testing some newer approaches to treatment that may help doctors target tumors more precisely. This should allow development of more effective treatments that cause fewer side effects. Although these treatment approaches are promising, most are still experimental at this time and are only available through clinical trials.
As researchers have learned more about the gene changes that help tumor cells grow, they have developed newer drugs that target these changes. These targeted drugs work differently from standard chemotherapy drugs.
One example of such a targeted drug is everolimus (Afinitor), which may shrink or slow the growth of subependymal giant cell astrocytomas (SEGAs) that can’t be removed with surgery (see “Targeted therapy for brain and spinal cord tumors in children”).
Some types of medulloblastomas tend to have mutations (changes) in genes that are part of a cell signaling route called the hedgehog pathway. The hedgehog pathway is crucial for the development of the embryo and fetus, but it can be overactive in some medulloblastoma cells. Drugs that target proteins in this pathway are now being tested against medulloblastoma in clinical trials.
Several other targeted drugs are already being used to treat other types of cancer, and some are being studied to see if they will work for brain tumors as well.
Tumors have to create new blood vessels (a process called angiogenesis) to keep their cells nourished. New drugs that attack these blood vessels are used to help treat some cancers, including some brain tumors in adults. Several drugs that impair blood vessel growth are now being studied for use against brain tumors in children.
Hypoxic cell sensitizers
Some drugs increase the oxygen content in the tumor, which makes tumor cells more likely to be killed by radiation therapy if they are given before treatment. Studies are now looking to see if this affects the outcome of treatment.
The goal of immunotherapy is to make the body’s immune system fight the brain tumor more effectively.
Several types of vaccines are being developed against brain tumor cells. Unlike vaccines against infectious diseases, these vaccines are meant to help treat the disease instead of prevent it. The goal of the vaccines is to stimulate the body’s immune system to attack the brain tumor cells.
Early study results of some of these vaccines have shown promise, but more research is needed to determine how effective they are. At this time, brain tumor vaccines are available only through clinical trials.
Other types of drugs that affect the immune system, such as lenalidomide, are also being studied.
Researchers have done a great deal of lab work with viruses that reproduce only within brain tumor cells and then cause those cells to die, while leaving normal cells alone. Research using these viruses in humans with brain tumors is still in the earliest stages.
Last Medical Review: 03/22/2013
Last Revised: 01/31/2014