A brain tumor is a tissue or mass of abnormal cells in the brain resulting from uncontrolled cell division as new ones replace damaged or old ones. The rate of growth and spread of brain tumors vary greatly. A tumor is either benign (non-cancerous or unlikely to spread) or malignant (cancerous). Due to the limited space in the skull, any tumor can interfere with brain and body functions. The type, location, size and growth rate of a tumor determines how it affects these functions and how it can be treated.
Types of Brain Tumors
Brain tumors can broadly be classified as either benign or malignant depending on their rate of growth and spread. Benign brain tumors grow slowly, rarely spread and have distinct boundaries. The cells in a benign tumor are non-cancerous, but the tumor may be life-threatening if located in a vital area of the brain. Malignant brain tumors grow rapidly, spread quickly to nearby brain areas and have irregular boundaries. While a malignant brain tumor is sometimes called brain cancer, it does not fit the true definition of cancer because it does not spread to organs outside the brain and spinal cord.
Tumors of the brain are also classified according to area of origin as either primary or metastatic (secondary). Primary brain tumors occur when abnormal growth begins in the brain itself or in surrounding tissues such as cranial nerves, pineal gland, pituitary gland or meninges (brain-covering membranes) and the tumor does not spread to other parts of the body. A primary brain tumor can be benign or malignant. Metastatic (secondary) brain tumors occur when cancers that begin in other parts of the body spread to the brain. While any form of cancer can spread to the brain, the most common ones resulting in secondary brain tumors are breast cancer, kidney, lung or colon cancer and melanoma.
Primary Brain Tumors
Primary brain tumors are rare and occur much less frequently than metastatic (secondary) brain tumors. When they occur, primary brain tumors are named according to the cells affected. Examples of primary brain tumors include:
- Gliomas: A range of tumors that start in the glial cells of the brain or spinal cord. They include astrocytomas, glioblastomas, ependymoma, oligodendrogliomas and oligoastrocytomas.
- Meningiomas: Tumors that start in the membranes (meninges) surrounding the brain or spinal cord. They are common in adults 40-70 years old, often in women, but are mostly non-cancerous.
- Schwannomas (acoustic neuromas): Benign tumors that occur in nerves controlling hearing and balance. They tend to affect adults 40-70 years old and are found in men and women.
- Pituitary adenomas: Tumors that grow in the pituitary gland just underneath the brain. They are mostly benign tumors, but affect the production of pituitary hormones.
- Medulloblastomas: Cancerous brain tumors that begin in the lower back portion of the brain and spread through spinal fluid. They are common in children, but rare in adults.
- Primitive Neuroectodermal tumors (PNETs): Rare tumors found in fetal or embryonic brain cells. They can occur in any area in the brain.
- Craniopharyngiomas: Rare, non-cancerous tumors that begin near the pituitary gland, but spread gradually affecting the pituitary gland and various other structures around the brain.
- Germ cell tumors: These tumors tend to occur during childhood in the areas where the testicles or ovaries are formed, but they sometimes spread or move to other body parts, including the brain.
Who Is Affected By Brain Tumors?
According to the American Brain Tumor Association, around 80,000 primary brain tumors are diagnosed every year in the United States. Secondary (metastatic) brain tumors are more common, with between 200,000 and 300,000 cases of secondary tumors recorded in the U.S. every year. Unfortunately, around 170,000 Americans die of brain tumors every year, with children ages 3-12 and adults ages 40-70 being the most affected. It is estimated that 20 to 40 percent of all cancer patients suffer from brain tumors, with secondary brain tumors outnumbering primary brain tumors by 10 to 1.
Causes and Risk Factors of Brain Tumors
The causes of primary brain tumors are still unclear. In fact, medical science is yet to establish the causes or prevention of tumors that begin in the brain. Nevertheless, some factors that increase the risk of brain tumors have been identified. These include:
- Age: While brain tumors can occur at any age, they are more common in adults ages 40-70 or older. Still there are specific types of brain tumors that are found almost solely in children.
- Having a cancer elsewhere in the body: Cancer of the kidney, colon, breast or skin may lead to brain cancer due to spread of the cancer to the brain.
- Exposure to radiation: Exposure to ionizing radiation increases the risk of brain tumor. Ionizing radiation causing brain tumors includes the radiation used in cancer therapy and that emitted from atomic bombs. Other forms of radiation such as radiofrequency radiation from microwave ovens and cellphones and electromagnetic fields of power lines have not been shown to cause brain tumors.
- Prolonged exposure to industrial solvents, pesticides and other chemicals.
- Inherited disorders such as neurofibromatosis or turcot syndrome.
- Family history: A small fraction of brain tumors are found in people with a family history of genetic syndromes increasing the risk of brain tumors or families whose members have a history of certain brain tumors.
Brain Tumor Signs and Symptoms
Brain tumors are all potentially life-threatening regardless of whether they are malignant, benign, primary or metastatic. Since the brain is enclosed within a bony skull and cannot expand to create room for the extra mass, brain tumors tend to compress and displace normal tissue, cause swelling (edema), block the flow of cerebrospinal fluid (CSF), increase intracranial pressure and enlarge the hydrocephalus (ventricles). The increased size, swelling and pressure result in a number of symptoms, depending on the location, type and size of the brain tumor.
Common symptoms include:
- Headaches that worsen when sleeping, waking up, or making abrupt movements such as coughing.
- Unexplained vomiting or nausea.
- Seizures in people with no history of seizures.
- Dizziness, stumbling or trouble walking.
- Difficulty with balance and coordination.
- Hearing problems
- Difficulty with speech
- Loss of vision or abnormal eye movements.
- Numbness, weakness or loss of movement or sensation in a leg or arm.
- Bladder control problems.
- Changes in personality, mood or behavior.
- Cognitive difficulties such as confusion, disorientation or memory loss.
Diagnosis of Brain Tumor
When a doctor suspects that you have a brain tumor, the following will be performed to diagnose the condition:
- Personal and family history: Used to evaluate your degree of risk for brain tumors.
- Physical examination: Used to assess your overall health.
- Neurologic examination: Includes checking your hearing, vision, balance, coordination, reflexes and strength. Used to evaluate the function of your brain and spinal cord in order to provide clues to the specific area that is affected by the brain tumor.
- Imaging studies: The most commonly used imaging tests are computer tomography (CT) scan, magnetic resonance imaging (MRI) and positron emission tomography (PET). These tests are used to determine the location, type, size and extent of spread of a brain tumor. CT scan is invaluable for diagnosing metastatic brain tumors.
- Electroencephalogram (EEG): Study of the brain’s electrical impulses in order to determine how a tumor is affecting the brain.
- Biopsy: When scans do not provide a clear picture of a brain tumor, a small amount of the affected tissue can be removed and examined by a pathologist under a microscope to diagnose the tumor.
Cerebrospinal fluid (CSF) may also be examined for cancer cells.
Treatment of Brain Tumors
After it has been confirmed that you have a brain tumor, the doctor will decide on appropriate treatment depending on your age, tumor type, tumor size, its location, extent of spread of the tumor, your preferences, your overall health and other health factors. Since there are many kinds of brain tumors, with some being highly complex, many specialist doctors may be involved in your treatment. The team may include an oncologist, neurosurgeon, radiologist, radiation oncologist, neurologist and neuro-ophthalmologist. Treatments may be used in combination with the goal of removing all or as much of the tumor as will reduce the chance of a recurrence.
Treatment options include:
- Observation: When diagnosed with a benign and slow-growing brain tumor with just a few symptoms, your doctor may decide on being observed actively with routine MRI scans annually until the tumor grows or shows symptoms that require treatment. Doctors tend to recommend observation for older patients (70 years or more) who have other problematic health conditions.
- Medication (Chemotherapy): Depending on your brain tumor, the doctor may use drugs to kill tumor cells and eliminate symptoms. The drugs can be taken orally, applied as a wafer on a tumor or injected into your vein. Common drugs for treating brain tumors include temozolomide, lomustine and carmustine. A drug such as dexamethasone may be used to reduce or prevent inflammation and swelling around the brain tumor, mannitol or furosemide may be used to prevent intracranial pressure and edema, while an anticonvulsant such as phenytoin, valproic acid, carbamazepine or levetiracetam can be used to control or prevent seizures.
Targeted drug therapy: This technique uses specific drugs to target particular abnormalities of cancer cells to kill the cells. For example, the brain tumor called glioblastoma can be targeted using bevacizumab (Avastin), which stops new blood vessels from forming, cuts off blood supply to the tumor and kills tumor cells. Likewise, the drug everolimus (Afinitor) treats a benign brain tumor common in people with tuberous sclerosis by blocking the enzyme pathway responsible for the growth of the cancer cells.
- Radiation therapy: Also called radiotherapy, radiation therapy is the use of controlled amounts of high-energy rays to safely and effectively kill tumor cells, control tumor growth or relieve brain tumor symptoms. The radiation damages the DNA of cancer cells, rendering them incapable of multiplying while also killing them. Dead cancer cells are eliminated naturally from the body while healthy cells around the treated tumor will repair and multiply after treatment. There are two types of radiation therapy for brain tumors: external beam radiotherapy and brachytherapy (internal radiation therapy). External beam radiation is typically delivered from outside the body using a machine that directs high energy radiation (gamma rays, X rays) at the brain tumor. It comes in three forms: stereotactic radiosurgery (SRS), fractionated stereotactic radiotherapy (FSR) and whole brain radiotherapy (WBRT). Brachytherapy (internal radiation) is delivered from inside the body by surgically placing a radioactive material directly into a tumor.
- Surgery: Used to treat a brain tumor located in a place that can be accessed without causing significant injury to any vital part of the brain. A neurosurgeon can open the skull to remove the whole tumor or just to remove a portion of the tumor if it is located near vital areas of the brain. Often the removal of even a small portion of the tumor will relieve the symptoms. But surgery also can be performed to release intracranial pressure or refine diagnosis. When only a portion of the brain tumor is removed, chemotherapy or radiation is used to treat the remaining cancer cells. Nowadays, advancements in surgical techniques such as functional brain mapping, intraoperative MRI/CT and image-guided surgery have ensured that surgeons can precisely locate tumors, define tumor borders, confirm amount of tumor already removed and avoid injuring vital brain areas.
- Adjunct therapies: Newer treatments for brain tumors are still being developed. For example, biotherapy or immunotherapy is a technique used to activate your immune system (antibodies and T-cells) to destroy tumor cells, gene therapy introduces new genetic material into brain tumor cells in order to kill them, while hyperbaric oxygen improves tumor healing, fights infection and boosts tumor responsiveness to treatment. More options are available and your doctor will recommend the most appropriate for your condition.
Recovery from Brain Tumor
Before treatment, your doctor will discuss with you any side effects of the treatment option chosen. Potential side effects include skin irritation, hair loss, visual changes, headaches, fatigue, unsteadiness, nausea and vomiting. The doctor also will discuss with you any home care measures that should be taken by you and your family to accelerate recovery. If the brain tumor has affected your speech, vision, motor skills and thinking, the doctor probably will recommend that you go for physical therapy, occupational therapy, speech therapy or other necessary rehabilitation essential for your recovery. Follow your doctor’s advice strictly.