A "tame" virus could prove to be a future weapon against prostate cancer, early research suggests.
Scientists who administered the virus to six volunteer patients found it killed off cancer cells while sparing normal tissue.
The respiratory, enteric, orphan virus, or "reovirus" is widespread but causes no significant illness in humans.
People exposed to it suffer, at most, mild flu-like respiratory symptoms or diarrhoea.
Previous research has shown that reovirus has "oncolytic" potential, meaning it preferentially targets cancer cells.
There is already some evidence of its effect against lymphoid, ovarian, breast, pancreatic and high grade glioma brain cancers.
The new Canadian study is the first to test the virus on prostate cancer.
Study leader Dr Don Morris, from the Tom Baker Cancer Center in Alberta, said: "Our results are a stepping stone into future prostate cancer clinical trials with another category of cancer therapeutics."
The researchers recruited six men with early-stage prostate cancer that had not yet started to spread.
Each was given a single injection of the virus into their tumour, guided by ultrasound.
Three weeks later the patients had their prostate glands removed as part of their normal treatment.
Analysis of the prostate tissue showed the death of cancer cells in the treated tumours. However there was no sign of the virus replicating in non-cancerous areas of the prostate.
"For the treatment of localised prostate cancer, we found that the reovirus is safe and has evidence of specific tumour versus normal prostate cell efficacy," said Dr Morris.
The findings were reported today in the journal Cancer Research.
Professor Robert Clarke, a member of the journal's editorial board, said: "People have known of this application of the reovirus in trials, but no-one to my knowledge has conducted trials in prostate cancer.
"I think this is an interesting approach. There is not a lot done in oncolytics, but clearly it is an area that is getting increasing attention, and we need everything we can get our hands on to make a difference in these patients."
Each year around 35,000 men in the UK are diagnosed with prostate cancer and 10,000 die from the disease.Reuse content