There is always research going on in the area of brain tumors. Scientists are looking for causes and ways to prevent brain tumors, 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 recently 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 in the short term to help decide which children might need more or less intensive treatment. In the future, doctors may be able to develop and use drugs that specifically target these gene changes.
Imaging and surgery techniques
Recent advances have made surgery for brain tumors much safer and more successful. Such techniques include:
- Functional magnetic resonance imaging (fMRI), which can identify the site of important areas of the brain and how close they are to the tumor.
- Image-guided surgery, which allows for safer and more extensive removal of the tumor.
Radiation therapy
Several newer types of radiation therapy now allow doctors to 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.
Chemotherapy
New approaches may help make chemotherapy more useful against brain and spinal cord tumors.
Adjuvant chemotherapy
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 very good responses to this very intensive treatment, others have had 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 under way to determine how useful it is.
Modification of 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 and clinical trials.
Getting chemotherapy directly to tumors
Some new approaches may allow doctors to 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 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. In theory, this should allow for more effective treatments that cause fewer side effects. Although these treatment approaches are promising, most are still in the experimental stage at this time, and are generally only available through clinical trials.
Targeted drugs
Tumor cells are often very sensitive to proteins called growth factors, which cause them to grow and divide. Newer drugs target some of these growth factors, which may slow the growth of tumor cells or even make them die. One example of such a targeted drug is everolimus (Afinitor), which may shrink or slow the growth of subependymal giant cell astrocytomas that can't be removed with surgery. 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.
Angiogenesis inhibitors
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, although it's not yet clear if they will help 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.
Immunotherapy
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.
Therapeutic viruses
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.
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