Genetically engineered herpes virus can help successfully cure patients with head and neck cancer, doctors have found.
A London hospital trial of 17 patients has shown that use of the virus along with chemotherapy and radiotherapy helped kill the tumours in most patients.
Study leader Dr Kevin Harrington, of Institute of Cancer Research in London, said current treatments were effective if the cancer was diagnosed early.
The herpes virus is genetically modified in such a way that it grows inside tumour cells but cannot infect normal healthy cells.
Once there it has a triple effect - it multiplies, killing tumour cells as it does so, it is engineered to produce a human protein that activates the immune system and it also makes a viral protein that acts as a red flag to immune cells.
In the 17 patients injected with the virus, in addition to their standard treatment, 93 percent showed no trace of cancer after their tumour had been surgically removed.
More than two years later, 82 percent of patients had not succumbed to the disease.
According to Clinical Cancer Research only two of 13 patients given the virus treatment at a high dose relapsed.
"Around 35 to 55 percent of patients given the standard chemotherapy and radiotherapy treatment typically relapse within two years, so these results compare very favorably," the BBC quoted Harrington as saying.
Dr Alison Ross of Cancer Research UK said it would be some time before the treatment could be used in patients, as it still needed to be tested directly against standard treatment.
But she added: "This small study highlights the potential of using genetically modified viruses as a weapon to fight cancer."