Cancer and the Brain
What is Cancer ?
Cancer is a disease of the body’s cells. Our bodies are constantly making new cells: to grow, to replace worn-out ones, or to heal damaged ones after an injury. Normally, cells grow and multiply in an orderly way. Occasionally, however, some cells behave abnormally. They multiply in an uncontrolled way, and these abnormal cells may grow into a lump, which is called a tumour.
Tumours can be benign (not cancerous) or malignant (cancerous). Benign tumours do not spread outside their normal boundary to other parts of the body. A malignant tumour is made up of cancer cells. If these are not treated they may spread into surrounding tissues.
If the abnormal cells spread beyond their normal boundaries then the tumour is malignant, that is it is a cancer.
How Cancer Spreads
Sometimes cells break away from the original (primary) cancer and spread to other organs. When these reach a new site in the body, they may continue to grow and form a new tumour on that site. This is called a secondary cancer or metastasis.
In some cancers, it is the body’s blood cells, which multiply abnormally. These cancers are called leukaemias, myelomas and lymphomas.
The average brain weighs about one and a half kilograms and is surrounded and protected by the skull. The brain controls how the body functions. Centres within the brain control mechanical things such as body movement, circulation of the blood, and breathing. There are also areas of the brain, which enable us to feel sensations such as pleasure or pain. The brain controls speech, memory and learning, and it is the source of our emotional responses, behaviour and personality. It also controls the release of hormones in the body.
The brain is largely made up of nerve cells, or neurones. We are born with about 40 billion of them, which must serve us for life because, unlike all other cells in the body, nerve cells do not replace themselves. The nerve cells communicate with each other and with other parts of the body by sending messages (or nerve impulses, which are actually very small electric currents) through a complex system of nerve pathways.
The brain contains four cavities filled with fluid called cerebrospinal fluid. The fluid, which is made in these cavities flows through narrow passages between the cavities and the surface of the brain. Occasionally this flow can be blocked by a brain tumour; the fluid is dammed up in the brain, and as more fluid is made, the pressure rises. This is called hydrocephalus and it is common in children with brain tumour.
A brain tumour is a mass of unnecessary and abnormal cells growing in the brain. A tumour that starts in the brain is a primary brain tumour, which in turn may be grouped into “benign” and “malignant” tumours.
Primary brain tumours rarely spread outside the brain and spinal cord. In order to be labelled a cancer, a tumour must have the ability to metastisize and spread to other organs of the body. Primary brain tumours rarely behave this way.
However, cancer cells which begin growing elsewhere in the body and then travel to the brain, form metastatic brain tumours. All metastatic brain tumours are malignant since they begin as cancer elsewhere in the body.
A benign tumour consists of very slow growing cells, usually has distinct borders, and rarely spreads. Treatment and/or surgery is often effective, however, if a benign tumour is located in a vital area of the brain, it can be considered life threatening.
A malignant brain tumour is life threatening, invasive, and usually rapid growing. This is in contrast to other malignant tumours of the body that are invasive but grow more slowly.
Benign brain tumours can cause problems by pressing on and damaging the surrounding brain tissue; however, they can often be successfully removed.
Malignant brain tumours, or brain cancers, vary widely both in the way they grow and the way they respond to treatment. Some are neatly contained within a capsule (encapsulated) and relatively easy to remove. Others have long, thin filaments spreading through the brain, like roots of a plant.
Many malignant tumours in the brain are secondary cancers. Your doctor will be able to tell you wether yours is a primary or secondary tumour. It is rare for primary brain tumours to spread to other parts of the body.
Brain tumours are generally named for the tissue in which they arise. Names of different types of brain tumours include: gliomas (astrocytomas, oligodendrogliomas, ependymomas and mixed cell type gliomas), meningiomas, medulloblastomas, chordomas glioblastomas and central nervous system lymphomas.
Spinal cord cancers
The spinal cord is the main trunk of nerves leaving and entering the brain, on their way to and from all parts of the body. The spinal cord extends from the base of the brain to just below the waist. It is about as thick as a little finger and is protected by the spinal column (backbone). Tumours are less likely to develop in the spinal cord than in the brain, and most cancers affecting the spinal cord will have spread from a primary cancer elsewhere in the body.
A tumour on the spinal cord may stop the flow of messages along the nerves between the brain and body, in much the same way as accidental injury to the spinal cord does. More commonly a tumour, usually a secondary cancer, in the spinal column (that is, in the bone surrounding the spinal cord) will affect the spinal cord by pressing on it.
Pain is a common symptom, as the tumour presses on the spinal cord in its narrow space within the backbone. Loss of feeling and loss of movement in legs and arms may follow.
To diagnose a spinal tumour the doctor will need to examine you carefully and you will need to have x-rays of the affected spinal areas taken. The doctor may also order a Magnetic Resonance-Imaging (MRI) scan.
Prompt treatment may prevent or lessen the affects of spinal cord tumours. Surgery is the usual method of treatment. Radiotherapy and chemotherapy may be used in conjunction with surgery.
Cancers that occur high in the spinal cord are classified with brain tumours.
Causes of brain tumours
The causes of brain cancer are not fully understood. Research, including research funded by the Brain Foundation, is being undertaken at a number of Australian research institutes.
Source: Anti-Cancer Council of Victoria “Brain Cancer: A Guide for People with Cancer, Their Families and Friends”