It's the world's first clinical trial for a vaccine against brain cancer and it's happening in Oregon.
Researchers and neurosurgeons from Providence Medical Center in Portland believe they are using the bacteria Listeria to train the body to reject cancer cells.
The team added two cancer-specific genes to the listeria strain, transforming a once harmful bacterium into a potential powerful tool in the fight against cancer.
"The surgeon can almost never get all of it out," said Keith Bahjat, a researcher at Providence Cancer Center. "The radiation can almost never get all of it out. That's why it almost always re-occurs in these patients.
"That's why is immunotherapy is so powerful. Because the immune system can differentiate between those tumor cells and normal cells and can just pick those off without damaging the surrounding brain tissue."
They have already enrolled three patients in the first phase of the trial.
The median life expectancy for brain cancer patients is 14 months.