A harmless virus that lives in the human respiratory and gastrointestinal tracts could be an important tool in the fight against cancer.

A team of British researchers, including a Maltese doctor, have found that reovirus magnifies the effects of radiotherapy in patients with advanced untreatable cancers.

Particles of reovirus are contained in a new drug, Reolysin, which is currently being tested on a number of patients at Britain's Institute of Cancer Research.

Early results have suggested that the drug, together with radiotherapy, could reverse the potentially deadly disease.

But one of the lead researchers, Maltese doctor Johann de Bono, warned against too much hype over the new drug, which has been described by British media as a "magic bullet" cure for cancer.

"At present we have some very interesting preliminary results that are promising but there is little evidence that the drug does anything on its own," Dr de Bono, a well-respected cancer researcher who has led many studies in the field, told The Times yesterday.

Dr de Bono explained that he used the drug on its own in more than 100 people and never saw a significant effect.

"In this trial, we gave the virus to patients together with radiotherapy, so it is hard to know what is working, whether the drug or the radiotherapy," he said.

The trial in question was done in 23 patients with a range of tumours in their lungs, bowels, ovaries and skin and who had stopped responding to traditional therapies but got some pain relief through radiotherapy. The tumours either shrank or stopped growing in each case.

Although the results are promising, Dr de Bono said this virus was surely not a magic bullet to treat cancer. He said there was still not enough evidence on whether it would make it in the long term and have any effect on patients.

"It is interesting and there have been promising preliminary results but there is still a lot of work to be done," he said, adding that work would continue.

In fact, the next step is to investigate the effects of the combination of Reolysin and radiotherapy in newly-diagnosed cancer patients.

Dr de Bono, originally from Birżebbuġa, said a lot of work was currently underway using viruses to treat cancer, describing this as an innovative approach.