Brain Tumours & their Management
Since the brain is contained within a rigid skull, a tumor growing in the brain will eventually cause pressure and subsequent damage on adjacent normal brain. The symptoms depend on the size and location of tumor, as well as the mass effect caused by the abnormal space-occupying lesion. Symptoms may include headaches, nausea and vomiting, seizures, weakness, and confusion or difficulty concentrating. Since these symptoms may be caused by other medical conditions and a brain tumor cannot be seen or felt during a routine medical examination, your doctor may order an imaging examination. The most commonly used tests to detect brain tumors are the CT (or CAT) and MRI scans.
Types of Malignant Brain Tumors
These tumors arise from star-shaped cells called astrocytes that normally serve as supportive tissue for brain cells. These tumors may behave with different degrees of malignancy or invasiveness that may be described as low-grade, mid-grade or high-grade, or, alternatively as grade I to grade IV. The most life threatening type of astrocytoma is grade IV and is also known as glioblastoma multiforme. Astrocytomas may occur in several different parts of the brain, such as the cerebral hemispheres containing the frontal, parietal, temporal and occipital lobes, in the brainstem when it is called a
brainstem glioma, or in part of the visual pathway when it is called an optic nerve glioma.
CNS lymphoma may affect previously healthy individuals or patients who have compromised immune systems. These tumors are treatable with radiation.
This tumor type arises from cells that usually form the lining of the fluid-filled cavities of the brain. Ependymomas may occasionally spread to another location in the central nervous system or originate in the spinal cord.
Glioblastoma Multiforme (GBM)
This malignant brain tumor is the most common primary brain tumor that occurs in adults. Its insidious biological behavior makes the treatment of this tumor type extremely difficult.
Medulloblastomas are the second most common type of brain tumor in children but may also occur in adults. These tumors are located in the cerebellum and may cause symptoms of clumsiness, headaches and nausea.
Metastatic Brain Tumors
Metastatic brain tumors occur more frequently than primary brain tumors. These malignant brain tumors are formed by cancer cells that originated from a cancer growing in a separate organ of the body before spreading to the brain. The malignant tumors that spread most often to the brain are lung cancer, breast cancer, skin melanoma, and renal (kidney) cancer. Metastatic brain tumors may be single or multiple and can occur in the cerebral hemispheres or cerebellum.
Treatment of Malignant Brain Tumors
The currently available treatment options for malignant brain tumors include surgery, radiosurgery, chemotherapy, radiation therapy and immunotherapy, which may be employed in different combinations depending on the type of malignant brain tumor, stage of disease and overall health.
This is the treatment of choice for accessible brain tumors, which are located in areas of the brain that may be removed without great potential of neurological damage. The goals of surgery are: 1) to remove as much of the tumor as possible so there will be less of a tumor burden for adjuvant therapies, 2) to provide tumor tissue for microscopic examination in order to reach an exact diagnosis in order to guide additional treatment, and 3) to provide direct access to the malignant tumor cells for other treatments, such as implants for gene therapy. If surgical removal is not immediately feasible or if the tumor is inaccessible, that is, in an area of the brain that is deep and inoperable, then a stereotaxic biopsy may be performed to establish a diagnosis. This is a minimally invasive procedure whereby computer guidance allows a probe to reach almost any area of the brain through a small hole in the skull.
Many tumors consist of cells that die after exposure to radiation. Radiosurgery utilizes a single, high dose of radiation delivered to a discrete, well-defined area.
Conventional radiation therapy employs external beams of x-rays or gamma rays produced by a machine called a linear accelerator or a cobalt machine aimed at the tumor or when necessary, the entire brain. Radiation therapy may be given over a period of several weeks.
Chemotherapy utilizes drugs to poison and kill malignant tumor cells. There are many drugs that can destroy brain tumor cells, but each particular tumor may consist of cells with different drug sensitivities. Therefore, chemotherapy is usually administered as a combination of drugs in order to maximize the damage to the malignant tumor cells and minimize the overall toxicity to the body. Chemotherapy drugs may be administered into the veins of the body, that is intravenously, taken in pill form by mouth, or delivered directly into the central nervous system by means of implanted drug reservoirs and pumps, or drug-saturated wafers placed into the brain after the tumor has been surgically removed.
The body’s natural defense system against disease is the immune system. Immunotherapy recruits the body’s natural disease-fighting mechanisms to mount an attack against malignant brain tumor cells. The agents of immunotherapy are called biological response modifiers, which are substances that either suppress tumor cells directly or stimulate the body to produce anti tumor factors.
Despite treatment with conventional therapies such as surgery, radiation and chemotherapy, malignant brain tumors nearly always recur. As a result, a number of experimental therapies have been devised to treat malignant brain tumors after they have grown back. The experimental therapies that are currently available include gene therapy, experimental chemotherapy, chemotherapeutic drugs delivered by implantable wafers (Gliadel wafers), and infusion of immunotoxins directly into the brain tumor. These treatments are continuously undergoing analysis and revisions to assure their safety and efficacy. New treatments undergoing laboratory development and testing will be available in the near future.
The management of malignant brain tumors requires highly individualized considerations and goals. In order to maximize quality of life an optimal treatment strategy draws upon the multifaceted skills of a team consisting of neurosurgeons, neurologists and neuro-oncologists.
Brain tumors are made of cells growing and reproducing in an uncontrolled fashion.
A benign brain tumor is formed from abnormal cells that form a distinct boundary from the surrounding normal brain.
A malignant brain tumor is dangerous because it consists of cancerous cells growing into adjacent brain tissue so that it may no longer function normally.
The life threatening nature of a malignant brain tumor depends on both the type of cancerous cells that comprise the tumor and the exact location of the tumor in the brain.
Tumors that arise from cells found normally in the brain are primary brain tumors while metastatic brain tumors are formed by cancer cells originating from a cancer in another part of the body such as lung or breast cancer.