Neurosurgical Research Foundation

Tumours

Malignant glioma is the most common primary brain tumour. It affects young adults in the prime of their life and we see about 50 cases a year in South Australia .

Early results of glioma surgery were poor, and in the early 1900’s even the best surgeon had an operative mortality of 30%. The average survival was a matter of weeks to a few months. Modern anaesthetic and operative techniques have reduced the operative mortality but the overall prognosis has changed very little over the past few decades. The average life expectancy is till under a year.

One of the problems one faces when dealing with gliomas is determining the extent of the tumour. When CT was first introduced it was felt that this would define the limits of the tumour and allow curative surgery. This was not the case however and similar results have been found with MRI. We have studied the correlation between MRI and neuropathology in gliomas and found considerable diversity within a particular tumour with regard to its appearance on MRI. In some areas the abnormal area on MRI defines the tumour very well but in other areas of the same brain the tumour spread is grossly underestimated by the MRI and tumour can even spread to the opposite hemisphere and remain undetected. This has significance in both surgical and non-surgical treatment of gliomas. Even if one removes all of the abnormal brain as defined by MRI there will still be tumour left behind. Not only that but standard radiotherapy fields which include a 1-2 cm margin around the radiologically abnormal area will also miss active tumour. A glioma that is too small to detect on CT (less than 5mm) can grow to a mass of several centimetres diameter within four weeks, explaining why surgical removal of large amounts of tumour makes little or no difference to the prognosis.

It is generally accepted that the successful treatment for glioma will relay on differentiating tumour cells from normal cells using some cellular characteristic rather than an anatomical one. The treatment should be able to reach all cells of the brain but only kill those that carry the abnormality that defines them as malignant. Malignant glioma cells contain many abnormalities in their genetic make-up, including extra or deficient chromosomes, additional, altered or deficient genes and altered proteins consequent upon this. Some of these abnormalities have been shown to be fairly specific for gliomas and others are found in a wide variety of tumours. Research is in progress all over the world to determine which markers best define the tumour cells and how they can be targeted and selectively killed.

Other Tumours

Malignant tumours that have spread from cancer in other parts of the body are easier to distinguish from the normal brain. Newer methods of radiotherapy (radiosurgery), using very accurate targeting of high doses of radiation are being used with considerable success for those tumours that are not removable surgically.

Benign tumours do not spread to other parts of the body like malignant tumours and usually grow much more slowly. Benign brain tumours can still cause significant morbidity and mortality however, because there is only a finite amount of space in the skull and as they enlarge they cause pressure on the brain. Some benign tumours are being treated with radiosurgery, particularly acoustic neuromas, which grow on the nerves to the ear and cause deafness.

Another common benign brain tumour is the meningioma. These are more common in females and have been shown to contain various hormone receptors, raising the possibility treating them with tablets to block these hormones, as is done with breast cancer. Indeed, epidemiological research has demonstrated an association between breast cancer and meningioma.

The treatment of pituitary tumours has also changed over recent years due to advances in neurosurgical research. Most pituitary operations are performed through the nose rather that through the skull and endoscopy is increasingly being use. The most common type of pituitary tumour is now often treated with tablets instead of surgery.