In a ground-breaking advance, French neurosurgeons on Friday said they had successfully treated brain tumours through ultra-keyhole surgery, using a tiny fibre-optic laser to destroy cancerous cells.

Alexandre Carpentier of the Pitie-Salpetriere Hospital in Paris said the exploit was "a world-first" in its use of multiple advanced techniques and of local anaesthesia rather than general sedation.

So far, eight volunteers have been treated in the pilot programme, launched December 2006, Carpentier told AFP.

"They were suffering from metastasing brain tumours caused by various cancers, mainly lung and breast cancer that failed to respond to conventional treatment and were otherwise inoperable," he said.

Doctors had given the volunteers only three months left to live, on average.

Under the pioneering technique, a minute hole three millimetres (0.12 of an inch) wide was drilled into the skull, allowing the surgeon to introduce a water-cooled fibre-optic laser into the brain.

The device was gently guided towards the tumour area with the help of a magnetic resonance imaging (MRI) scanner.

Every three seconds, a computer workstation calculated the temperature at the area being burned by the laser to ensure that there was no dangerous overheating and to confirm that only tumorous cells were being destroyed.

The patient received only a local anaesthetic, remaining conscious in order to be able to speak to the medical team to help verify that cerebral functions were not being harmed.

However, "the patients feels nothing during the operation and generally can leave hospital 14 hours later, the evening or the morning after the operation," the surgeon said.