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Clinical trials
Not all patients are cured with standard therapy, and some standard treatments may have more side effects than are desired. As a result, some people with brain tumors participate in clinical trials. Clinical trials are research programs conducted with patients to evaluate new medical treatments, drugs, or devices. They are ongoing in most parts of the country for most types of adult or pediatric brain tumor. Some of the therapies being studied include:
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Immunotherapy:
This uses the immune system, the body's natural defense against infection and disease, to fight cancer. Immunotherapy uses substances made by the body or made in a laboratory to boost, dirUgh.ect, or restore the body's natural defenses against disease. In theory, the body's immune system should recognize tumor cells as abnormal and then attack and destroy them. This immune surveillance probably occurs daily and destroys many early tumor cells. A tumor cell might develop, however, that can fool the immune system by making substances that block the signals that tell the immune system to seek and destroy the abnormal cells. Or the body's immune system might be weakened by HIV infection, drugs, or alcoholism and allow tumor cells to escape control.
Animal studies have shown that a healthy immune system that is being fooled by the tumor can be taught to recognize the tumor and resume its control duties. Researchers have been working on a variety of brain tumor vaccines that teach the patient's immune system to attack a previously cloaked primary tumor.
Immunotherapy represents a promising new class of treatments that, in theory, could confer lifelong immunity to a variety of tumors affecting the brain. Other promising means of using the immune system to treat tumors include tagging potent toxins to antibodies (immunotoxins) that selectively seek out the tumor cell, so that only the tumor cells receive the poison, delivered through slow, continuous infusion over several days. This process is called
convection-enhanced delivery.
Gene therapy:
The goal of gene therapy is to repair or replace the defective genes that may be causing a tumor to grow. Perhaps the most appealing means of curing brain tumors is to correct the underlying defects in the genes that direct tumor control. Genes that promote growth could be turned off, those that suppress growth could be turned on, defective monitoring mechanisms could be turned on, genes that produce a beacon for the immune system could be delivered, and so on. Gene therapy has been used successfully in mice to rid them of primary and secondary tumors. The principal problem with gene therapy as the primary treatment of brain tumors is that, in theory, every tumor cell must be treated with gene therapy. If even one cell escapes, it could regrow into a large tumor.
While it is possible to inject enough reparative genes into a tumor in a mouse to eradicate the tumor, it is quite a different thing to inject enough gene therapy into a human brain tumor, which is likely to be much larger. To date gene therapy has been shown to kill human tumor cells; unfortunately, current delivery mechanisms are inefficient and unable to deliver enough to cure the whole tumor. Nonetheless, gene therapy might well become an important future treatment of human brain tumors, alone or in combination with the above therapies.
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