BRAIN TUMOURS

WHAT IS A BRAIN TUMOUR?

A brain tumour is a mass of abnormal cells that are proliferating (growing) too rapidly and in an uncontrolled manner within the cranial cavity (skull). Commonly, these tumours grow within the substance of the brain itself but may grow from tissues outside the brain and indent the brain (e.g. meningioma). In this section I will discuss tumours growing within the brain.

Tumours growing within the brain may be primary intrinsic tumours, having arisen from any cell type present within a normal brain (see brain anatomy), or they may be secondary tumours, having arisen from the spread of a malignant tumour (cancer) elsewhere in the body. Primary tumours most often arise from the supporting cells of the brain (glia) and are, therefore, termed gliomas. Secondary tumours may spread from any other cancer in the body but most often from lung, breast, abdominal and skin cancers. A secondary tumour is also called a metastasis.

WHAT SYMPTOMS DO BRAIN TUMOURS CAUSE?

Brain tumours present in 3 principal ways.

• Headaches - this is due to an elevation of the pressure within the skull caused by the expanding mass of the tumour and any swelling associated with it. These headaches are often worse at night, in the early hours of the morning and may sometimes be associated with vomiting or visual disturbance.
• Changes in function - due to damage to, or pressure on, certain areas of the brain. For example, a tumour in the right hemisphere might cause weakness of the left side of the body. Tumours in the frontal lobes might cause changes in personality or behaviour.
• Seizures (fits or epilepsy) - due to irritation of certain areas of the brain causing neurones to fire-off uncontrollably. These may be focal (partial) fits causing a jerking or twitching of one or more limbs, which is commonly followed by a period of paralysis in the affected limb (which then recovers). There may also be generalised fits (often termed an epileptic fit) in which there is loss of consciousness, twitching of all the limbs and often tongue biting and incontinence.

Sometimes tumours in the brain may be found by chance during a scan for another reason. Other lesions in the brain (blood clots, abscesses, inflammatory conditions, etc) can produce symptoms that are similar or identical to those produced by tumours.

HOW DO YOU DIAGNOSE A BRAIN TUMOUR?

If your doctor suspects you may have a brain tumour because you have some or all of the symptoms listed above, he will refer you for a scan of your brain. This might either be a CT scan or an MRI (see investigations). If there is any possibility of a secondary tumour (metastasis) your doctor might arrange other investigations including a chest X-ray, blood tests, and sometimes CT scans of your chest, abdomen and pelvis. The brain scan will show if there is any mass in the brain and will give a good idea of the type of lesion. However, a scan alone is not a completely reliable indicator of the precise diagnosis - this often requires a biopsy.

If your scan has demonstrated a mass in the brain, your diagnosis will usually need to be confirmed with biopsies sent from an operation. Your neurosurgeon may advise an open operation to resect the tumour (if it can be removed safely) or otherwise he may advise a biopsy of the lesion. The biopsy results will tell us the type of tumour (cell of origin) and the grade of the tumour (how fast it is growing) - this is essential information as different tumours require different types of treatment and carry different prognoses. Sometimes a biopsy will diagnose another condition rather than a tumour (e.g. abscess), which will clearly require a completely different treatment.

WHAT TREATMENTS ARE THERE FOR BRAIN TUMOURS?

There are many different treatments available for brain tumours, which depend on your precise diagnosis.

• Steroids - dexamethasone is a steroid drug that is prescribed for many patients with brain tumours as it is very effective at reducing swelling in the brain surrounding a tumour. It may improve your symptoms within 24 hours.
• Surgery - it is now possible to safely operate on most brain tumours. For some benign tumours (particularly those lying outside the brain e.g. meningioma), it may be possible to completely remove the tumour with an operation alone with a high chance of cure. However, for tumours within the brain (e.g. gliomas or metastases) it will usually not be possible to remove the tumour completely, therefore, other treatments are often needed post-operatively.
• Radiotherapy - some brain tumours respond to radiotherapy (X-ray treatment), which may be used after your tumour has been removed or after a biopsy. For most tumours, radiotherapy is used to slow the growth of the tumour and is not curative, however, there are some rare brain tumours that can be cured with radiotherapy.
• Chemotherapy - some brain tumours respond to chemotherapy (drug treatment), which may be used (after diagnosis) alongside radiotherapy or after radiotherapy. For most tumours, chemotherapy is used to slow the growth of the tumour and is not curative, however, there are some rare tumours that can be cured with chemotherapy.
• Radiosurgery - radiosurgery is the precise use of highly focused radiation treatment at high dose designed to effectively 'kill' the population of cells targeted (the tumour) without damaging the surrounding brain. It may be given with a gamma knife or LINAC-based technology. It can be used to cure some benign brain tumours and is also effective at treating cerebral metastases that are not operable.