BRAIN tumours could be cured by a tiny probe that heats cancer cells when inserted into the skull. The heat causes the tumour to coagulate, leaving the dead tissue to be removed by the body’s natural processes.
Surgeons can operate the probe with enough precision not to damage healthy areas of the brain around the tumour. Brain tumours are normally treated by surgery, after a section of the skull has been removed – a drastic procedure known as craniotomy.
In order to diagnose the type and severity of the tumour the surgeon has to take a biopsy through a small hole in the skull. In the new treatment a thin tube is inserted through the same bur-hole. The probe then passes an electric current through the tissue heating the tumour to 80 °C for one minute.
To ensure that the probe only touches the tumour the surgeon watches the operation on a video monitor which displays images obtained by interventional magnetic resonance imaging. This type of MRI allows the surgeon to stand next to the patient, to direct the probe to the tumour accurately and to see the results of the operation.
Yoshima Anzai, who has treated 15 patients, says, “MRI provides a very clear picture of the tumours during treatment and also has the advantage of giving us immediate feedback about the effect the treatment is having on the tumour”.
Anzai, assistant professor of radiology at the University of California in Los Angeles, believes that the treatment can cure some types of tumour, although she emphasises that it is still at an early stage. She says the technique, which she calls radio-frequency ablation, is most successful on small tumours of less than 3 centimetres in diameter because treating a larger tumour could cause swelling in the surrounding brain tissue, which could in turn cause complications.
Tumours with a small supply of blood vessels respond better to the technique than those with a rich supply because the blood vessels carry the heat away making it more difficult to destroy the tumour. In nine of those treated by Anzai there was no recurrence of the tumour one year after treatment but six had tumours that had spread from other parts of the body. Secondary tumours in the brain are often treated with radiation therapy and four of the successfully treated cases had undergone previous radiation therapy that had failed to work.
Anzai says that the treatment takes up to three hours. It can be performed with a local anaesthetic and people only needed to be kept in hospital for 24 hours. Patients who have a tumour removed by conventional surgery have to spend at least one week in hospital. The technique also had the advantage that it could be repeated without causing damage.
Anzai acknowledges that it is not suitable for all types of brain tumour. Some tumours can extend beyond the area that shows up on MRI and consequently the treatment does not destroy all the cancer cells.
“Although further study is needed, MRI-guided radio-frequency ablation has the potential to replace surgery or other traditional treatments as the therapy of choice for certain patients,” says Anzai.