The trial is part of a series of international studies into the reovirus
Cancer patients in Leeds are taking part in a trial which could lead to the development of a new treatment for the disease, a research professor has said.
Professor Alan Melcher of Leeds University is leading a team which is investigating how a virus, called a reovirus, kills cancer cells.
Patients at the city's St James's University Hospital are being given the virus before undergoing operations.
Their tumours will then be examined to see how the virus targets cells.
Prof Melcher, who is leading the research, said: "The reovirus is a natural virus that all of us have been exposed to at some time in life.
"For reasons that are not entirely clear it kills cancer cells. It is now being tested on patients to see if it can have a significant effect, and improve and prolong people's lives."
Prof Melcher said the reovirus appeared to have fewer side effects than chemotherapy and radiotherapy.
He said it was "a possibility" that the virus could be used as a future treatment for the illness.
"So far it seems to be very well tolerated - people are managing it very well," he added.
The trial is one of a number of international studies into the reovirus.