brain cancer

There are two types of brain tumors: primary brain tumors that originate in the brain and metastatic (secondary) brain tumors that originate from cancer cells that have migrated from other parts of the body.
Primary brain cancer rarely spreads beyond the central nervous system, and death results from uncontrolled tumor growth within the limited space of the skull. Metastatic brain cancer indicates advanced disease and has a poor prognosis.
Primary brain tumors can be cancerous or noncancerous. Both types take up space in the brain and may cause serious symptoms (e.g., vision or hearing loss) and complications (e.g., stroke).
All cancerous brain tumors are life threatening (malignant) because they have an aggressive and invasive nature. A noncancerous primary brain tumor is life threatening when it compromises vital structures (e.g., an artery).


Incidence and Prevalence
In the United States, the annual incidence of brain cancer generally is 15–20 cases per 100,000 people. Brain cancer is the leading cause of cancer-related death in patients younger than age 35.
Primary brain tumors account for 50% of intracranial tumors and secondary brain cancer accounts for the remaining cases. Approximately 17,000 people in the United States are diagnosed with primary cancer each year and nearly 13,000 die of the disease. The annual incidence of primary brain cancer in children is about 3 per 100,000.
Secondary brain cancer occurs in 20–30% of patients with metastatic disease and incidence increases with age. In the United States, about 100,000 cases of secondary brain cancer are diagnosed each year.

Types of Brain Cancer
The World Health Organization (WHO) has nine categories of primary brain tumors, which are based on the types of cells in which the tumors originate. Gliomas are primary brain tumors that are made up of glial cells—cells that provide important structural support for the nerve cells in the brain.
Infiltrative astrocytoma and glioblastoma multiforme (GBM) account for nearly 85% of all brain tumors, with the remainder spread among the other seven types.
Tumor Type Cell Origin
Infiltrative astrocytoma Astrocytes
Pilocytic astrocytoma Astrocytes
Oligodendroglioma Oligodendrocytes
Mixed oligoastrocytoma Oligodendocytes and astrocytes
Glioblastoma multiforme (GBM) Astrocytes and other brain cell types (astroblasts, spongioblasts)
Ependymoma Ependymocytes
Medulloblastoma Primitive neural cell
Meningioma Meninges
Other
Tumor grade: All gliomas, except GBM, range from well-differentiated tumors (low grade) to anaplastic, that is, completely chaotic, undifferentiated (high grade). High-grade tumors are more aggressive and are associated with lower survival rates. In terms of surviving the disease, the grade of the tumor is the most important feature.
Primary Tumors
A primary brain tumor usually develops through a complex series of molecular and cellular mutations and may take years to acquire enough mass to cause symptoms that bring the disease to a person's and/or a physician's attention.
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* astrocytoma–most common type of brain tumor in children; originates in the brainstem, cerebellum, white matter of the cerebrum, or spinal cord
* brainstem glioma–originates in the medulla, pons, or midbrain
* choroid plexus papilloma–originates in the ventricles
* ependymoma–originates in the membrane that lines the bentricles and central canal of the spine
* glioblastoma multiforme–most common types in adults; originates in glial cells in the berebrum
* medulloblastoma–second most common type in children; originates in the fourth cerebral ventricle and the cerebellum; often invades the meninges
Other types of primary brain cancer include the following:
* acoustic neuroma–originates in the vestibulocochlear nerve
* lymphoma–originates in lymphocytes; common in HIV/AIDS patients
* meningioma–originates in the meninges
* pineal gland tumor–rare; originates in the pineal gland
* pituitary adenoma–originates in surface cells of the pituitary gland
* schwannoma–originates in cells of the myelin sheath that covers neurons
Secondary (Metastatic) Brain Tumors
In adults, the most common types of cancer that spread to the brain are the following:
* melanoma
* breast cancer
* renal cell carcinoma
* colorectal cancer
The prognosis for people who develop brain metastases is generally poor.
Causes and Risk Factors
Aside from a known association with exposure to vinyl chloride, there are no known chemical or environmental agents that lead to the development of brain tumors.
Genetic mutations and deletions of tumor suppressor genes (i.e., genes that suppress the development of malignant cells) increase the risk for some types of brain cancer. Inherited diseases that are associated with brain tumors include the following:
* Multiple endocrine neoplasia type 1 (pituitary adenoma)
* Neurofibromatosis type 2 (brain and spinal cord tumors)
* Retinoblastoma (malignant retinal glioma)
* Tuberous sclerosis (primary brain tumors)
* Von Hippel-Lindau disease (retinal tumor, CNS tumors)
Patients with a history of melanoma, lung, breast, colon, or kidney cancer are at risk for secondary brain cancer.
Exposure to vinyl chloride is an environmental risk factor for brain cancer. Vinyl chloride is a carcinogen, that is, a cancer-causing substance. It is used in manufacturing plastic products such as pipes, wire coatings, furniture, car parts, and housewares, and is present in tobacco smoke.
Manufacturing and chemical plants may release vinyl chloride into the air or water, and it may leak into the environment as a result of improper disposal. People who work in these plants or live in close proximity to them have an increased risk for brain cancer.
Signs and Symptoms
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A brain tumor can obstruct the flow of cerebrospinal fluid (CSF), which results in the accumulation of CSF (hydrocephalus) and increased intracranial pressure (IICP).Nausea, vomiting, and headaches are common symptoms.
Brain tumors can damage vital neurological pathways and invade and compress brain tissue. Symptoms usually develop over time and their characteristics depend on the location and size of the tumor. A brain tumor in the frontal lobe may cause the following:
* Behavioral and emotional changes
* Impaired judgment
* Impaired sense of smell
* Memory loss
* Paralysis on one side of the body (hemiplegia)
* Reduced mental capacity (cognitive function)
* Vision loss and inflammation of the optic nerve (papilledema)
A tumor located in both the right and left hemispheres of the frontal lobe often cause behavioral changes, cognitive changes, and a clumsy, uncoordinated gait.
A tumor in the parietal lobe may cause the following symptoms:
* Impaired speech
* Inability to write
* Lack of recognition
* Seizures
* Spatial disorders
Vision loss in one or both eyes and seizures may result from a tumor located in the occipital lobe.
Tumors that develop in the temporal lobe are often asymptomatic (i.e., without symptoms), but some may cause impaired speech and seizures.
A tumor in the brainstem may produce the following symptoms:
* Behavioral and emotional changes (e.g., irritability)
* Difficulty speaking and swallowing
* Drowsiness
* Headache, especially in the morning
* Hearing loss
* Muscle weakness on one side of the face (e.g., head tilt, crooked smile)
* Muscle weakness on one side of the body (i.e., hemiparesis)
* Uncoordinated gait
* Vision loss, drooping eyelid (i.e., ptosis) or crossed eyes (i.e., strabismus)
* Vomiting
Ependymoma originates in the lining of the ventricles and the spinal canal and may damage cranial nerves. When this happens, hydrocephalus, stiff neck, head tilt, and weakness may result.
Symptoms produced by a tumor of the meninges (meningioma) depend on which area of the brain is being compressed. They include:
* Headache
* Hearing loss
* Impaired speech (i.e., dysphasia)
* Incontinence
* Mental and emotional changes (e.g., indifference, disinhibition)
* Prolonged drowsiness (somnolence)
* Seizures
* Vision loss
A tumor located in the pituitary gland (i.e., pituitary adenoma) may increase the secretion of hormones and cause discontinuation of menstruation (i.e., amenorrhea) and excess secretion of milk (i.e., galactorrhea) in women. Impotence may occur in men.
Brain Cancer Diagnosis
The first step in diagnosing brain cancer involves evaluating symptoms and taking a medical history. If there is any indication that there may be a brain tumor, various tests are done to confirm the diagnosis, including a complete neurological examination, imaging tests, and biopsy.
Imaging Tests
Magnetic resonance imaging (MRI scan) is the diagnostic test of choice for brain cancer. ELectromagnetic energy produces detailed computer images of the brain from different angles. It can detect edema (swelling of brain tissue) and hemorrhage (bleeding). In some cases, a dye is injected intravenously to improve the contrast between an abnormal mass and normal tissue.
Computed axial tomography (CAT or CT scan) involves the use of x-rays and a computer to obtain images of the brain. A dye is often injected intravenously to improve the contrast between an abnormal mass and normal tissue. Not only can the tumor be seen, but the type of tumor sometimes can be identified with a CT scan.
Positron emission tomography (PET scan) helps the physician evaluate brain function and cell growth by producing images of physical and chemical changes in the brain. An injected radiopharmaceutical substance is absorbed by tumor cells in the brain. Measurements of brain activity are determined by concentrations of the substance and then fed into a computer, which produces an images of the brain.
PET can precisely locate a tumor and detect metastatic and recurrent brain cancer at earlier stages than MRI or CT scan. This technique also can be used to evaluate the tumor's response to chemotherapy and radiation treatment.
Biopsy
Examination of tumor tissue is the only way to arrive at an exact diagnosis of the tumor. In a biopsy, a small part of tumor tissue is removed surgically and then sent to a lab, where a pathologist examines it.
The type of tumor is determined by the type or types of cells (called grading) seen under the microscope, and, if malignant, the stage–that is, the degree of invasiveness, the growth rate, and the cancer cells' similarity to normal cells–is also determined.
In stereotactic biopsy imaging tests are used to locate the tumor, a small hole is made in the skull, and a hollow needle is passed through to obtain a core of tumor tissue. Examination of the sample provides an accurate diagnosis in over 90% of cases.
Possible complications resulting from the procedure include blood clot, hemorrhage, and infection. The rate of complications is very low, about 3%.
Treatment
Treatment for brain cancer depends on the age of the patient, the stage of the disease, the type and location of the tumor, and whether the cancer is a primary tumor or brain metastases. The treatment plan is developed by the oncology team and the patient.
Treatment involves any combination of surgery, radiation, and chemotherapy. Some tumors require several different surgical procedures, and some can be treated with radiation alone.
Surger
Surgery is the treatment of choice for accessible primary brain tumors, when the patient is in good health. The goal of surgery is to remove as much of the tumor as possible without damaging nearby normal brain tissue. The prognosis improves when more than 90% of a tumor can be removed.
Removal is often complicated by the nature of the tumor (e.g., invasive, highly vascularized) and by its location. Partial removal (debulking) of the tumor can improve quality of life by alleviating symptoms and sometimes improve the effectiveness of radiation therapy or chemotherapy.
Before surgery, some important tests are performed. Patients over the age of 40 usually undergo an electrocardiogram (ECG or EKG) and a chest x-ray. Other tests are used to detect the presence of uncontrolled hypertension, diabetes, active coronary ischemia, or the presence of circulating anticoagulant (substance that inhibits normal blood clotting) in the blood. If any of these conditions are present, it may not be advisable to undergo craniotomy.
Craniotomy
Craniotomy is the treatment of choice and the goal is to remove as much of the tumor as possible. The procedure is performed under general anesthesia and involves opening the skull (cranium).
The neurosurgeon makes an incision into the scalp and several holes (called burr holes) are made in the skull. A bone saw is used to join the holes together to create a flap of bone.
The bone flap is then removed to expose the brain and remove as much of the tumor as possible. After the tumor has been partially or completely resected, the bone flap is replaced and secured using fine wire. Recovery from the procedure may take as long as 8 weeks.
Complications of craniotomy include bleeding (hemorrhage), swelling (edema), increased intracranial pressure (IICP), infection, and brain tissue damage.
In laser microsurgery, MRI is used to pinpoint the location of the tumor and a laser is used to destroy the tumor. This procedure may be used after craniotomy to remove remaining tumor tissue.
Brain-mapping is performed under local anesthesia and sedation. Electrodes stimulate nerves in the brain, measure responses, and allow communication with the patient. The surgeon removes as much of the tumor as possible without damaging vital areas of the brain, such as those that control motor function and speech.
In some cases, a chemotherapeutic agent called BCNU is used following surgery. In this treatment, the neurosurgeon places a wafer soaked with BCNU (Gliadel®, BiCNU®) into the surgical cavity after the tumor has been removed. By applying it directly to the diseased area of the brain, side effects are limited and the drug has a more beneficial effect.
Postoperative care includes drug therapy with corticosteroids, histamine inhibitors (block stomach acid), and antiepileptics. Corticosteroids (dexamethasone and Decadron®) help reduce swelling and can relieve various postoperative neurological effects.
An MRI scan, with and without contrast, is often obtained to determine the extent of residual disease following surgery. Sometimes, a plan for rehabilitation is needed.
Radiation Therapy
Radiation is used when the entire primary tumor cannot be surgically removed. Most malignant brain tumors are treated with external-beam radiation even if the entire primary tumor is surgically removed, because hidden tumor cells often remain in brain tissue.
The survival rate for patients with malignant tumors (e.g., anaplastic astrocytoma, glioblastoma multiforme) more than doubles with radiation therapy, and it can prolong life for patients with low-grade gliomas as well.
Radiation therapists use several different approaches to treat primary brain tumors, but external-beam radiation is the most common. Local radiation therapy techniques, including external focal, brachytherapy, and stereotactic radiosurgery, may be administered to selected patients.
There are various other radiation techniques, some of which are being used on an experimental basis. An assortment of technologies, as well as the use of medications and other compounds, can make tumor cells more sensitive to radiation.
External-beam radiation
External-beam radiation, the traditional form of radiation therapy, delivers radiation from outside the body. Therapy usually begins a couple of weeks after surgery and is typically repeated at regular intervals for several weeks.
Hyperfractionation is a modified form of external-beam radiation that involves applying less intense but more frequent doses of radiation. Some benign tumors are treated with external-beam radiation to prevent recurrence, even if the entire primary tumor has been surgically removed. They also may be treated with radiation at the time of recurrence.
Stereotactic radiosurgery
Stereotactic radiosurgery delivers radiation to the tumor in a single dose and does not involve surgery, as the term may imply. In this procedure, a head frame supporting a CT or MRI scanner may be attached to the skull. With the aid of computer imaging, the radiologist is able to pinpoint the exact location of the tumor and aim the beam of radiation directly at it.
Some tumors, however, cannot be treated with the intense local radiation of radiosurgery. For example, tumors near the optic nerves are better treated with several small doses, because the optic nerves are especially sensitive to radiation. These tumors may be treated using stereotactic radiotherapy. Stereotactic radiotherapy involves applying many small doses of radiation, using the same imaging techniques used in stereotactic radiosurgery.
Newer stereotactic techniques usually do not involve the use of the head frame. Radiation often is delivered from several different directions, hitting the tumor at various angles. The advantage of using localized radiation is that the surrounding, healthy tissue is left undestroyed. This treatment may be used in addition to external-beam radiation, especially in cases of malignant gliomas and mestastases that are in deep or sensitive areas of the brain. Types of machines that are used to perform stereotactic radiosurgery include the Gamma knife® and modified linear accelerators (LINAC; e.g., CyberKnife®).
The Gamma knife uses ioninzing beams of radiation (called gamma rays) that are sent from different angles and come together at a single point on the tumor. Each beam is low dosage; however, when they converge, the intensity and destructive power is high. This treatment is used to treat small tumors.
Linear accelerators (e.g., CyberKnife®) involve using small doses of radiation over multiple sessions (called fractionated stereotactic radiotherapy). In this treatment, which allows larger tumors to be treated, the patient is positioned on a bed that can be moved, providing flexible positioning. Linear accelerators produce positively-charged atoms (called protons) in patterns that are matched to the size and shape of the tumor and used to destroy cancer cells.
Brachytherapy
Brachytherapy involves implanting capsules containing radioactive substances into the tumor to deliver localized radiation. It is frequently applied to treat recurrent disease in an area previously treated by external-beam radiation.
Advantages of this type of radiation therapy include sparing vital structures close to the tumor and a shorter length of treatment (i.e., hours to days instead of weeks).
Radiation follow-up
Because loss of pituitary function can be a long-term side effect of radiation therapy, an endocrine evaluation is an important part of follow-up care for patients who have received radiation. Neuropsychological testing may also be done to evaluate whether a patient has incurred diminished intellectual activity resulting from brain tumor radiation.
Chemotherapy
Generally, tumors are satisfactorily treated with radiation and/or surgery. Chemotherapy is not used for benign tumors and is generally not a very effective treatment for most malignant primary brain tumors or metastatic tumors.
The problem with chemotherapy is that it works by interrupting mitosis, the process of cell division. Many brain tumors grow slowly by nature, so slowing their growth by chemotherapy doesn't do much good. Another problem with chemotherapy is that there are few chemical agents that can cross the blood-brain barrier and get to the tumor.
The capillaries and arteries in the central nervous system are unlike the vessel walls found in the rest of the body, which allow proteins and large organic molecules to pass out of the bloodstream and into tissues. Vessel walls in the CNS allow only water, small solutes, and simple gases such as oxygen and carbon dioxide to pass into brain tissue. While this protects the brain from exposure to chemical flux in the body, it also creates a barrier against many therapeutic agents, making chemotherapy problematic.
Chemotherapy uses chemicals that are designed to poison tumor cells, but it's difficult to know which chemicals will reach which tumors. So, a combination of chemicals is usually used to treat a brain tumor.
Some cancer cases require chemotherapy after surgery and radiation. Chemotherapy is also used as a radio-sensitizing agent with radiation to control a recurrent tumor and to treat patients who can no longer tolerate radiation therapy.
Overall, studies have shown that patients who receive chemotherapy for malignant tumors have improved survival rates compared to patients who do not. The effectiveness of chemotherapy depends on the tumor type (medulloblastomas, anaplastic astrocytomas, and glioblastomas respond in varying degrees).
Chemotherapy is often used in very young children to delay radiation therapy for as long as possible. Some meningiomas respond to antiprogesterone agents. Most mestastatic brain tumors do not respond to chemotherapy, although there are exceptions. For these, the best chemotherapy agent is usually the one that has been the most effective with the primary cancer.
Agents that commonly work in patients with high-grade gliomas include procarbazine, platinum analogs (cisplatin, carboplatin), the nitrosureas, and an oral medication called Temodar® (temozolomide). In March 2009, the U.S. Food and Drug Administration (FDA) approved an intravenous (IV) form of temozolomide.
One chemotherapeutic agent that has proved to be effective is BCNU. The neurosurgeon places a wafer soaked with BCNU (Gliadel®, BiCNU®) into the surgical cavity after the tumor has been removed. By applying it directly to the diseased area of the brain, side effects are limited and the drug has a more beneficial effect.
Chemotherapy agents being tested for use in recurrent glial tumors include Taxol® (paclitaxel), irinotecan, topotecan, and high-dose tamoxifen with either carboplatin or procarbazine. Other chemotherapeutic agents for the treatment of recurrent gliomas include interferon and retinoic acid.
There are many experimental treatments, ranging from novel chemotherapeutic agents to drug therapy to new ways of applying radiation, that your neurologist, neurosurgeon, radiation oncologist or neuro-oncologist can discuss with you. As with any serious illness, it is generally a good idea to understand your options, get a second or third opinion, and gather as much information as you can about your particular case.
Other Treatments
An assortment of other treatments are commonly used when a brain tumor fails to respond to surgery, radiation, or chemotherapy. These involve the use of angiogenesis inhibitors—drugs that disrupt the blood vessels in a tumor, thereby cutting off a tumor's supply of nutrients and oxygen; differentiating agents—drugs that convert dividing cancer cells into mature, nondividing cells, thereby stopping further tumor growth; immunotherapy—various techniques that attempt to boost a person's immune system so that it more effectively fights the tumor cells; and gene therapy—inserting genes into tumor cells or the immune system to change the way the tumor cells operate.
Rehabilitation
Because of the effect that a brain tumor or treatment has on how a person functions, rehabilitation is an important part of recovery. Occupational rehabilitation involves restoring normal daily functioning, from working with one's hands to driving. Physical therapy involves improving a strength and motor function. Speech and language therapy may be important for restoring the ability to speak clearly. Cognitive therapy may be important for helping one deal with short-term memory loss.
There are specialists available to help with vision, balance, or facial paralysis problems. Sometimes patients need vocational therapy to help them return to the working world.
Self-help
It is a good idea to look for a support group and/or a counselor or psychotherapist to help deal with the stress and emotional challenges of living with, and recovering from, a brain tumor. Maintaining a positive attitude and taking care of one's emotional well-being are very important. It is improtant to exercise and a establish a healthy diet in order to feel well.