A mass created by growth of abnormal cells or uncontrolled proliferation of cells in the brain. Proliferation means rapid reproduction of tissue. Cancer cells are very prolific; they have high rates of cell division and growth.
An Overview of Brain Tumors
Cancer can occur in the brain in either of two ways: as a primary tumor (one that originates in that area) or as a metastasis (a secondary tumor that spreads from a cancer elsewhere in the body). The cause of primary brain tumor is unknown. Some tumors (retinoblastoma, for example) tend to be hereditary. Others tumors (craniopharyngioma) are congenital. Tumors may occur at any age, but many have a particular age group in which they are more common. The most common childhood brain tumors are astrocytoma, medulloblastoma, ependymomas, and brain stem glioma. Gliomas account for 75% of brain tumors in pediatrics, but only 45% in adults. Outside of retinoblastoma, most brain tumors are rare in the first year of life. Two-thirds of brain tumors in children are infratentorial with peak ages of 5 to 9 years. The annual incidence in children less than 15 years old is 2.4 per 100,000. More than 1,200 new cases occur each year. Another 80,000 people will be diagnosed with metastatic brain cancer. Cancers of the lung, breast, colon, and kidney, as well as malignant melanoma, are the most common origins of metastatic brain tumors. Brain tumors occur more often in adults than in children, but they are the second leading cause of cancer death in children.
"Tumor" is a general term for a swelling or new growth of tissue. Brain tumors may be "malignant" or "benign"; however, because the brain is enclosed in the skull, even benign tumors can be dangerous. The skull cannot expand to make room for a growing tumor, so the tumor may press on or damage delicate brain tissue. Therefore, even a benign brain tumor may behave in a malignant fashion and become life threatening. Some benign brain tumors can also eventually give rise to malignant cells. For these reasons, instead of "malignant" or "benign," brain tumors are usually described as being "high-grade" (rapidly growing) or "low-grade" (slowly growing).
There are many different types of brain tumors; most are defined according to the type of cells from which they arise. The most common brain tumors in adults are:
Malignant gliomas, including anaplastic astrocytoma and glioblastoma multiforme, which arise from supportive tissues in the brain Meningiomas, benign tumors that arise from the membranes that line the skull and enclose the brain
In children, the most common brain tumors are:
Causes of Brain Tumors
The causes of the vast majority of brain tumors are unknown. However, we do know that there is a higher risk of brain tumors in Children and the elderly.
People exposed to x-rays to the head for the purpose of treating diseases, such as cancer (but not including dental x-rays)
People with certain rare genetic disorders, including Li-Fraumeni syndrome (increased risk of glioma); von Hippel-Lindau disease (increased risk of hemangioblastoma); tuberous sclerosis (increased risk of astrocytoma); neurofibromatosis type 1 or "von Recklinghausens" disease (increased risk of glioma); and neurofibromatosis type 2 (increased risk of acoustic nerve tumor and Meningiomas)
People with disorders of the immune system, including congenital immune deficiencies, and immune systems compromised due to treatment for cancer, taking immunosuppressive drugs to prevent rejection of transplanted organs or cells, or having AIDS (which increases the risk of lymphoma in the brain)
Certain other symptoms that may be associated with this disease:
The Detection and Diagnosis of Brain Tumors
There are no screening tests to detect brain tumors early. Most tumors of the brain are, instead, detected on the basis of symptoms. Survival generally depends on the type of tumor and its location rather than on early diagnosis and treatment.
Brain tumors can be difficult to diagnose because they can cause a wide variety of symptoms, all of which could also be attributed to other diseases. The symptoms depend on the size of the tumor and its location. Common symptoms include headache; vomiting; mental or emotional changes; seizures; visual problems; difficulty speaking, walking, or writing; and partial paralysis. To diagnose a brain tumor, a doctor usually takes a complete medical history and conducts a neurological examination, as well as a MRI (magnetic resonance imaging) scan of the brain. Occasionally, a CT (computed tomography) scan is performed instead of a MRI scan. A biopsy of the tumor tissue, removal of the tumor or, in some cases, a lumbar puncture (spinal tap) is also performed to provide a definitive diagnosis. One exception is a deep-seated tumor of the brain stem of children called a pontine glioma, which is diagnosed by MRI and for which biopsy is not considered beneficial.
Treatment for Patients with Brain Tumors
Many brain tumors such as meningiomas, acoustic neuromas, and pituitary adenomas are curable. Others, although they might not be completely cured, can be controlled for long periods of time. Treatment includes surgery, chemotherapy, and radiation therapy. These therapies may be delivered alone or in combination.
Surgery is the treatment of choice for tumors that can be reached without causing severe damage to brain tissue. Improvements in surgical techniques in the last few years have made it easier and safer for surgeons to remove tumors while sparing healthy brain tissue.
New methods of radiation therapy have allowed in many institutions. Brachytherapy or "interstitial radiation therapy, "in which doctors use catheters to deliver radiation-carrying "seeds" directly into the tumor. Three-dimensional conformal radiation therapy, which allows doctors to map the exact location and shape of the tumor using various 3-D imaging techniques and then aim numerous highly focused radiation-treatment beams at the tumor from different angles. Normal tissues near the tumor get only a low dose of radiation from one or a few beams, while the tumor gets the larger dose of all the beams added together. (As beneficial as radiation therapy can be, children are not often candidates for this form of treatment because it can damage the developing brain, leading to intellectual impairment, particularly in children under the age of three.)
As with radiation therapy, researchers have also refined and expanded the use of chemotherapy in the treatment of brain tumors. In some cases, very high doses of chemotherapy are used to destroy the tumor, and the patient then receives a transplant of bone marrow or peripheral blood stem cells (stem cell "rescue") to replace marrow or stem cells also damaged by the drugs. (Bone marrow contains developing red blood cells, white blood cells, and platelets. Stem cells are cells that have the potential to develop into any one of these cell types.)
Chemotherapy is available for the following types of brain tumors:
Oligodendrogliomas and primary brain lymphomas: A regimen of high-dose chemotherapy followed by peripheral stem cell rescue in the treatment of patients with these tumors, which are particularly sensitive to chemotherapy. The goal is to use high doses of chemotherapy drugs as sole treatment to eradicate the disease. Patients who have excellent responses to chemotherapy are spared conventional radiation therapy, minimizing the potential for cranial irradiation to cause potential future problems in thinking and learning.
Astrocytomas: The more common brain tumors -- the malignant astrocytomas -- are less sensitive to conventional chemotherapeutic agents.
Meningiomas: Physicians are also exploring the use of a chemotherapeutic drug, hydroxyurea, as a promising new agent for patients with recurrent meningiomas. Although most meningiomas are benign tumors, their high rate of recurrence makes them extremely difficult to treat and, to date, there have been no effective chemotherapeutic drugs to treat this disease. Recent data suggest that hydroxyurea shows great promise in the treatment of this most common brain tumor.
Glioblastomas: The best available clinical candidate available against this type of tumor blocks intracellular communication pathways by targeting the receptor for the growth factor PDGF (platelet-derived growth factor). This receptor studs the surfaces of the cells of glioblastoma, an aggressive type of brain cancer.
Support and Survival Issues
Physical therapy, occupational therapy, speech therapy, and/or psychological therapy may help patients whose cancer or treatment has made it more difficult for them to move, manipulate objects, work, speak, or manage general daily activities, as well as for those whose illness has had a significant emotional impact. Social workers can help patients and their families locate the resources they need.
After treatment for brain tumors, patients are encouraged to report any related symptoms promptly and have examinations, imaging studies, and any appropriate laboratory tests at the intervals recommended by their cancer-care team to ensure that any recurrence is detected early.