DURHAM, NORTH CAROLINA — A new experimental treatment is using a modified version of a once-dreaded virus to fight against a deadly form of brain cancer.

Glioblastoma is a type of cancer that occurs in the brain or spinal cord that is typically treated using surgery, radiation therapy, or chemotherapy. It is an aggressive disease, with only a 12 to 18 month prognosis for those with grade 4 tumors.

According to a study published in the New England Journal of Medicine, Duke University researchers removed genetic code from the polio virus and replaced it with DNA from the rhinovirus, which causes the common cold.

The modified virus is then injected directly into the tumors of glioblastoma patients through a catheter.

Instead of replicating itself, it attaches to receptors on the surface of the cancer cells, infecting them and prompting the body's immune system to attack.

Of the 61 glioblastoma patients treated using the re-engineered virus, 21 percent are still alive three years later, compared to only four percent for those who underwent conventional treatment.

The experimental treatment, like many immunotherapies, had varied, sometimes dramatic effects on the subjects.

Scientists are still figuring out how to get the virus to produce the exact same results in different people, but are confident that it can be done.