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Chemotherapy is the use of anti-tumor drugs that slow or stop the growth of rapidly dividing cancer cells in the body. These drugs also kill these cells in some cases. It may be used for several different purposes in a cancer treatment plan, rounding out the trio of options for the treatment of brain tumors that also includes surgery and radiation.
Learn more on cancer chemotherapy and how it may affect you:
Types of chemotherapy drugs that may be used in treating brain tumors include:
- Conventional chemotherapeutic agents directed at dividing cells
- Targeted chemotherapeutic agents such as enzyme- or angiogenesis inhibitors or apoptosis inducers
- Intra-arterial Superselective Chemotherapy
- Immunotherapies such as monoclonal antibodies, cytokines, interleukins, interferons or cancer vaccines
- Novel agents in development
Using Chemotherapeutic Agents
Your doctor may want to use chemotherapy to achieve one or more clinical objectives, such as the following:
- Primary treatment to destroy cancer cells
- Before another treatment to shrink a tumor
- After another treatment to destroy any remaining cancer cells
- Relieve symptoms of advanced cancer
Chemotherapeutic drugs (also called chemotherapy agents) are administered in several different ways:
- Orally (by mouth as a pill or liquid)
- Intravenously (by infusion into a vein)
- Topically (as a cream on the skin)
- By direct placement (via a spinal tap or via injection into the brain fluid through a device placed under the scalp)
At Houston Methodist, we also use novel techniques to administer chemotherapy, such as direct injection into the arteries that feed a tumor and direct placement into the tumor using minimally invasive surgery.
Conventional chemotherapeutic agents generally exploit the fact that cancer cells are dividing rapidly, and attack cell division. However, some normal cell types that are dividing can also be harmed by these drugs, causing damage to healthy cells and unpleasant side effects, such as nausea, vomiting, hair loss, fatigue and mouth sores. If your doctor thinks that chemotherapy is the right choice for you, we will give you instructions for strategies to prevent or manage side effects throughout your treatment. In addition, doctors at Houston Methodist continue to seek ways to improve the delivery of chemotherapeutic agents and to develop new agents to better treat these tumors.
Targeted Chemotherapeutic Agents
In an effort to increase the specificity of chemotherapy against cancer cells, and spare normal cells, several new types of treatments have been developed. Collectively these treatments are referred to as “targeted therapy.” Normal cells go through a transformation process to become cancer cells. Then, they grow into tumors or spread throughout a body system. At Houstson Methodist, we have gained extensive knowledge about this transformation process from normal to cancerous cells. Targeted therapy disrupts this transformation process. The drugs attack certain parts of the cell and the signals needed for the cancer to develop and keep growing.
These drugs can be grouped by how they work or what part of the cell or process they target.
Some of the types of targeted chemotherapy drugs your doctor may consider are the following:
- Enzyme inhibitors – These drugs block enzymes that the tumor needs to grow. Blocking them may prolong your life and/or help other drugs to work better.
- Apoptosis-inducing drugs – These drugs kick off apoptosis, a normal process that causes cells to die.
- Angiogenesis inhibitors – These drugs block the tumor from creating the blood supply it needs to grow or spread.
Today many different types of targeted therapies are used to treat cancer and new ones are developed all the time.The two main types of targeted therapy drugs are:
Antibody drugs -- man-made versions of immune system proteins (called antibodies) designed to attack certain targets on cancer cells. The body normally makes antibodies to fight harmful invaders like germs.
Small-molecule drugs -- Since antibodies are large molecules, this other type of drug is called a “small-molecule” targeted therapy drug. These drugs are able to attach to very specific areas of cancer cells. Since they do not attach to normal cells, there are fewer side effects. These targeted therapies are often grouped as immunotherapies, or treatments that work with your immune system to fight cancer. But some of them act more like targeted therapy drugs. For example, bevacizumab acts as an angiogenesis inhibitor, and cetuximab and trastuzumab work like enzyme inhibitors.
Intra-arterial Superselective Chemotherapy
Chemotherapeutic drugs are most often given intravenously or orally. This can be an advantage if your doctor wants the drug to circulate throughout your body (systemically). But it also exposes normal cells to chemotherapy. Neuro-oncologists at Houston Methodist have been exploring innovative delivery approaches that make it possible to deliver higher doses to tumor cells and lower doses to normal cells.
Doctors at the Kenneth R. Peak Brain and Pituitary Treatment Center at Houston Methodist have a novel treatment for refractory malignant brain tumors: intra-arterial (IA) superselective chemotherapy. A first in the state of Texas, this treatment is used on brain tumors that are resistant to other therapies. Using this technique, chemotherapy drugs are directly infused into the blood vessels that supply the tumor. This type of therapy can deliver tens to hundreds of times higher drug levels to the cancer compared with standard intravenous infusion, but because the chemotherapy is delivered directly to the tumor, there are fewer side effects.
To further improve this technique, doctors at Houston Methodist have used intra-arterial treatment to first deliver a drug that opens the blood brain barrier (the mechanism that prevents potentially harmful drugs from crossing from the blood into the brain). The barrier is opened in the blood vessels directly supplying the tumor, and then IA superselective chemotherapy is given.
Based on published research and clinical experiences, IA superselective chemotherapy has been shown to be both safe and effective in controlling some malignant brain tumors. The technique uses tiny microcatheters that are threaded up from a vessel in the groin directly into the blood vessels supplying the brain tumor. Using this technique, Houston Methodist physicians can precisely target and deliver these drugs directly into tumor tissues.
A recent case involved a patient with an inoperable malignant brainstem glioma: The basilar artery that permeated the tumor and brainstem was catheterized by two separate microcatheters (very thin tubes). A balloon microcatheter was positioned past the location of the tumor and was inflated intermittently to reduce the amount of blood that flows away from the tumor, “persuading” the blood carrying mannitol (a diuretic drug) to overcome the blood brain barrier. The cancer drug bevacizumab, infused from a second microcatheter placed upstream, was able to flow directly into the tumor-containing tissue. The patient tolerated the treatment well, and the therapy killed tumor cells not responsive to standard treatments.
Immunotherapies rely on differences between your own normal cells and your cancer cells for their specificity. There are several different types of immunotherapies, some of which use your own immune system to fight the cancer, and some of which use chemicals from the immune system that are prepared in laboratories. Immunotherapies also differ with respect to how specific they are in killing cancer cells. Finally, the immune system can also be used to prevent cancer. Immunotherapy is a very active area of research, with advances emerging often.
Some of the currently available approaches to immunotherapy include the following.
- Monoclonal antibodies are man-made versions of immune system proteins. Antibodies can be very useful in treating cancer because they can be designed to attack a very specific part of a cancer cell, sparing normal cells.
- Cytokines are produced by cells of the immune system to communicate with other cells. They can help to control the growth or tumor cells and/or boost the activity of other immunotherapies, such as cancer vaccines. When used as “boosters” they are called immunomodulators.
- Interleukins are cytokines that act as chemical signals among white blood cells and boost immune responses. They may be used with other immunomodulators or to boost the response to vaccines.
- Cancer vaccines are substances put into the body to start an immune response against certain specific diseases. We usually think of them as being given to healthy people to help prevent infections, yet some vaccines may help prevent or treat cancer.
- Granulocyte-macrophage colony-stimulating factor is already used to help replace normal immune cells that are killed by chemotherapy, but it is not acting as a true immunotherapy in that setting. However, it is now being studied as a true immunotherapy.
Many other treatments are under development, some of which function as a result of totally new and different mechanisms. At the Houston Methodist Kenneth R. Peak Brain and Pituitary Treatment Center, we have several therapies in development and three novel therapies that will begin clinical trials soon.
- Mitochondrial smart bombs are a type of chemotherapy developed at the Houston Methodist Kenneth R. Peak Brain and Pituitary Treatment Center that can be selectively delivered into the powerhouse of the cell, the mitochondria. They have been highly effective against glioblastoma in experimental studies and are in the process of further development leading to clinical trials within the next 12 months to 18 months . They are the first known example of selective mitochondrial chemotherapy and hold great promise for treatment of malignant brain tumors.
- Nanosyringes are tiny syringes that make injections into individual cancer cells and spare normal cells. In experimental studies, they are highly effective against many types of cancer, including glioblastoma and breast cancer. They are also very close to clinical trials, in collaboration with Rice University.
- Drug pump inhibitors use nanosyringes to poison pumps inside tumor cells and prevent the cell from pumping out chemotherapy drugs. This attacks one of the main ways in which a tumor becomes resistant to chemotherapy, and therefore makes the chemotherapy used much more effective at a much lower dose.
Doctors at Houston Methodist are engaged in many clinical trials of drugs and other treatment options that are still in development. To find out more about active clinical trials related to brain tumors, please visit the following sites: