The therapy was tested on mice
Scientists are developing a viral smart bomb which destroys brain cancer cells without damaging surrounding healthy tissue.
The therapy, known as Delta-24-RGD, is thought to be the first treatment for malignant glioma, the deadliest form of brain cancer.
Laboratory tests on animals have produced such highly promising results that US cancer authorities hope to begin human trials late next year.
The work has been carried out by a team from the MD Anderson Cancer Center at the University of Texas.
Lead researcher Dr Juan Fueyo said: "We've never seen this kind of response before with any other treatment tested in either animals or humans.
"We believe this therapy has a lot of potential, but one that needs much more study."
Delta-24-RGD is designed in such a way that the virus can replicate only in cancer cells, which it kills in the process.
It moves on to contaminate other tumour cells, and when no more cancer cells are left to infect, the virus itself dies.
Dr Frederick Lang, who also worked on the study, said: "Biologic viral therapy like this may be just what we need to treat a complex disease like cancer.
"Cancer can be devious in that it does everything possible to evade destruction.
"But viruses are equally tricky in their quest to invade cells and propagate."
Tests were carried out on mice that had human glioblastoma tumours implanted in their brains.
More than half those that were treated with Delta-24-RGD survived for more than four months, whereas untreated mice lived for less than three weeks.
The treated mice were considered clinically cured of their brain tumours.
Investigators found only empty cavities and scar tissue where the tumours had once been.
Healthy cells are able to defend themselves against the virus because they produce a particular protein which prevents it from replicating.
However, glioma cells produce an ineffective version of this protein which renders them vulnerable.
Although the therapy targets only cancer cells, the researchers warn that human trials will be required before they can know for certain that it is safe.
There is a possibility that a small zone of healthy tissue around the tumour may be damaged.
In addition, nobody knows how the human immune system will respond to the introduction of a foreign virus.
The research is published in the Journal of the National Cancer Institute.