In two of the patients, the tumours disappeared. In a third, the tumour disappeared but recurred three months later. The lead doctor in the trial believes this may have occurred because the treatment dosage was too low.

The team of SGH doctors is ready to move to the next stage in September - a multinational trial involving 60 patients. This time, they will attempt to treat larger tumours of up to 5cm.

Liver cancer is extremely malignant and unless it can be completely removed through surgery, patients often die within months.

But some patients are too frail to survive an operation. Others may have so many tumours scattered around the liver that it is not possible to remove them surgically.

The treatment being tested at SGH involves nanotechnology.

A tiny radioactive silicon particle, BrachySil, is inserted into the tumour. Over a few weeks, the dust-size particle produces radiation that slowly kills the tumour around it.

BrachySil was developed by the British Defence Ministry and is owned by pSivida, a listed company that has the British government as its major shareholder.

But the idea of using the biodegradable silicon particle to treat liver cancer was the brainchild of doctors from SGH, which owns a small share in pSivida.

Using radiation to kill tumours is not new. The advantage of BrachySil is that it can be placed within the tumour so there is little damage to other organs.

Another advantage of BrachySil is that it is easily inserted, with the patient awake throughout the procedure, said Dr Pierce Chow, a senior surgeon specialising in liver operations.

BrachySil is also able to control the amount of radiation that bombards the tumour.

Because the malignant cells are killed slowly over several weeks, patients tolerate the treatment very well. If a tumour is killed off too quickly, the mass of dead cells in the liver could result in a raging fever and low blood count.

The next trial, which will involve cancer centres in countries like New Zealand and Vietnam, will be more aggressive.

Aside from treating bigger tumours, it will also increase the dose of radiation - up to three times the previous amount. This is to determine the ideal dose to remove the tumours.

Dr Anthony Goh, acting head of nuclear medicine at SGH and the principal investigator in the trial, said patients will be monitored closely to ensure they can tolerate the higher dose of radiation.

This trial will also test a multi-pronged inserter that can place three particles instead of just one into a tumour.

If all goes well, a larger trial will be done next year. This will be the final step before putting the treatment on the market.