Cancers of the central nervous system (CNS) are considered to be among the most devastating of all cancers. The brain and spinal cord are complex organs that control the CNS, the peripheral nervous system, and many of the voluntary and involuntary systems of the body. The effects can be devastating for the patient and the family when cancer attacks the CNS. It has been found that 20%–40% of all cancers metastasize to the brain (Cairncross, Kim, & Posner, 1980; Gavrilovic & Posner, 2005; Nathoo, Chahlavi, Barnett, & Toms, 2005; Posner, 1992).
All patients will have some change in personality, memory, motor skills, or executive functioning during the illness trajectory that compromises their quality of life. Care of those living with a brain and spinal tumor requires a broad knowledge base in neuro-oncology and a sensitive and realistic approach that optimizes quality of life and permits a sense of hopefulness to prevail. Care of informal caregivers also is an area of ongoing study. Risk Factors.
Little consensus exists regarding the risk factors for developing primary brain tumors. The general principles of tumorigenesis implicate an accumulation of inherited and acquired genetic alterations that allow cells to evade normal regulatory mechanisms and divide abnormally. The relationship between chromosome instability and cancer susceptibility is well established, as is the association of defective DNA repair mechanisms in individuals harboring chromosomal alterations (Busch, 1994; Wei et al. , 1996).
Heritable factors are implicated in a few rare autosomal dominant tumor syndromes (only one mutant gene is required to express the disease), including Li-Fraumeni syndrome, neurofibromatosis types 1 and 2, and Turcot syndrome (Ohgaki, 2009). Environmental factors associated with this malignant transformation have been difficult to positively identify. Exposure to ionizing radiation has been established as a risk factor for CNS tumors through studies on atomic bomb survivors, as well as children treated with radiation for tinea capitis (ringworm of the scalp) (Hodges, Smith, Garrett, & Tate, 1992; Preston et al. , 2002; Socie et al. , 2000).
The observation that brain tumor incidence is increased in certain occupations, including firefighters, physicians, farmers, embalmers, and pathologists, has prompted studies of the effects of industrial and occupational chemical exposure, but no definitive causative agent has been found (Mazumdar et al. , 2008). Studies on diet, alcohol consumption, tobacco, electromagnetic fields, and cell phone use have similarly resulted in conflicting and inconclusive findings about risk factors (Parascandola, 2001).
Some viruses have been implicated in brain tumor development in animal models, but only HIV has been causally linked to brain cancer in humans (Brittain, 2002; McLaughlin-Drubin & Munger, 2008). Radiotherapy * Radiation therapy may be given after surgery to slow or stop the growth of any remaining tumour cells. * External beam radiation is delivered to the tumour site using specialized techniques that direct a precisely focused beam of radiation at a small, defined target in order to minimize irradiation of adjacent tissue.
For gliomas, radiation is also directed at a margin surrounding the visible tumour, where microscopic tumours cells are most likely to be present. * Examples of these special types of radiotherapy include: Stereotactic Radiation Therapy (SRT), Intensity Modulated Radiation Therapy (IMRT), Three Dimensional Conformal Radiation Therapy (3D-CRT). * The radiation therapy dose may be divided into small doses and delivered over the course of several days or weeks. * Radiation therapy to the brain may cause short term effects such as fatigue, hair loss, and skin reactions, which generally clear up once the therapy is finished.
* Radiation to the brain may cause longer term side effects to memory, cognitive functions, and hormone production. * The BCCA has developed an information sheet for patients undergoing radiation to the brain Radiation exposure The best known environmental risk factor for brain tumors is radiation exposure, most often from some type of radiation therapy. For example, before the risks of radiation were recognized, children with ringworm of the scalp (a fungal infection) were sometimes treated with low-dose radiation therapy, which was later found to increase their risk of brain tumors as they got older.
Today, most radiation-induced brain tumors are caused by radiation to the head given to treat other cancers. They occur most often in people who received radiation to the brain as children as part of their treatment for leukemia. These brain tumors usually develop around 10 to 15 years after the radiation. Radiation-induced tumors are still fairly rare, but because of the increased risk (as well as the other side effects), radiation therapy to the head is only given after carefully weighing the possible benefits and risks.
For most patients with other cancers involving the brain or head, the benefits of radiation therapy far outweigh the risk of developing a brain tumor years later. The Anatomy of the Central Nervous System The central nervous system (CNS) is made up by the brain and spinal cord. This complex system controls both things that we intentionally think about and do, like walking and talking, and essential body functions that occur without specific thought on our part, such as breathing and digesting food. The CNS is also involved with the five senses of seeing, hearing, touching, tasting, and smelling, as well as emotions, thoughts, and memory.
The brain is a soft, spongy organ that is made up of nerve cells and tissue. It is divided into three major sections: the cerebrum, the cerebellum, and the brainstem. The cerebrum is the largest part of the brain, and is divided into two halves, called the right and left hemispheres. The right hemisphere controls the left side of the body and the left hemisphere controls the right side of the body. Each hemisphere is further divided into sections called lobes. There are four lobes in each hemisphere: the frontal, parietal, occipital, and temporal, and each lobe is responsible for certain functions.
* The frontal lobe is responsible for attention, thought, reasoning, behavior, movement, sense of smell, and sexual urges. * The parietal lobe is responsible for intellect, reasoning, the sensation of touch, response to internal stimuli, some language and reading functions, and some visual functions. * The occipital lobe is primarily responsible for vision. * The temporal lobe is responsible for behavior, memory, hearing and visual pathways, and emotions.
The cerebellum is much smaller than the lobes of the brain, and sits at the back of the brain under the cerebrum. It is responsible for balance and coordination and controls complex actions like walking and talking. The third part of the brain, the brainstem, connects the brain to the spinal cord. It controls some of the most important and necessary body functions, such as breathing and maintaining body temperature and blood pressure. It also controls hunger and thirst. The spinal cord is made up of bundles of nerve fibers, called vertebra. It starts at the base of the brain and extends a little more than halfway down the back.
Spinal nerves connect the brain with other nerves throughout the body and carry messages back and forth between the brain and the rest of the body. In order to protect the central nervous system from injury or damage, several protective barriers exist. Three thin membranes, called meninges, cover the entire brain and spinal cord forming a thin protective layer. In addition, a thin, watery fluid, called cerebrospinal fluid (CSF), cushions the brain and spinal cord and offers further protection. CSF is produced in four hollow spaces in the brain, called ventricles, and flows through the ventricles and in the spaces between the meninges.
It also brings nutrients from the blood to the brain and removes waste products from the brain. The bony structures of the skull and vertebra provide the final layer of protection for the central nervous system. Side effects Radiation therapy is in itself painless. Many low-dose palliative treatments (for example, radiation therapy to bony metastases) cause minimal or no side effects, although short-term pain flare-up can be experienced in the days following treatment due to oedema compressing nerves in the treated area.
Higher doses can cause varying side effects during treatment (acute side effects), in the months or years following treatment (long-term side effects), or after re-treatment (cumulative side effects). The nature, severity, and longevity of side effects depends on the organs that receive the radiation, the treatment itself (type of radiation, dose, fractionation, concurrent chemotherapy), and the patient. -he area of the patient’s body that is under treatment.
Modern radiation therapy aims to reduce side effects to a minimum and to help the patient understand and deal with side effects that are unavoidable. The main side effects reported are fatigue and skin irritation, like a mild to moderate sun burn. The fatigue often sets in during the middle of a course of treatment and can last for weeks after treatment ends. The irritated skin will heal, but may not be as elastic as it was before.