Viruses that have been genetically modified are the latest weapons to join the fight to destroy cancer cells.
The viruses travel through the bloodstream destroying the disease, which has spread but leaving healthy tissue undamaged.
They could eventually lead to a widespread treatment for cancers, which kill more than 150,000 people every year.
Professor John Bell, from Ottawa Hospital Research Institute in Canada, co-led a trial involving 23 patients.
"We're still in the early stages of testing these viruses in patients, but I believe that some day viruses and other biological therapies could truly transform our approach," the Daily Express quoted him as saying.
Tumours were seen to stop growing in six out of eight patients and the viral treatment avoids side-effects including hair loss, nausea, tiredness and diarrhoea common with chemotherapy.
The findings have been published in the science journal Nature.