Scientists in the United States say they have had complete success from trials on mice of a new vaccine aimed at preventing breast cancer.
Researchers at the Cleveland Clinic in Ohio say a single dose of the new vaccine administered to mice completely prevented the formation of breast cancer and stopped existing cancers from growing.
Their findings are published in the journal Nature and trials of the drug in humans are intended next.
But the researchers warn that it could be some years before any vaccine is widely available.
Immunologist Vincent Tuohy who led the research, said the vaccine targets a protein found in most breast tumours.
In the study, genetically cancer-prone mice were vaccinated - half with a vaccine containing an antigen called a-lactalbumin and half with a vaccine that did not.
The BBC reports none of the mice vaccinated with a-lactalbumin developed breast cancer, while all of the other mice did.