Researchers at Thomas Jefferson University have made significant strides toward developing a new way to treat the most common and most lethal brain tumor, glioblastoma.

The cancer is usually treated with surgery, followed by radiation and chemotherapy.

"Even with the best course of conventional treatments, life expectancy is in the area of a year and a half," said Craig Hooper, a cancer biologist at Jefferson.

The poor prognosis is why Hooper said researchers are focused on creating a new method.

Their novel procedure includes grabbing some tumor cells from a patient's brain, killing and treating them, and then encasing them in small plastic chambers that are reinserted into the patient's abdomen for a day.

When first tested for safety in a small pilot clinical trial back in 2001, two-thirds of participants saw their tumors shrink. The scientists didn't know why it might have worked, but guessed the immune system was behind it.

"The best chance of getting a tailor-made immune response that will go after the person's own tumor," Hooper explained, "is to use antigens from that tumor."

Tiny bits of the dying cancerous cells, the team has now learned, are key to that process. The particles, known as exosomes, leak out of small pores in the plastic chambers and go on to trigger the immune system to attack the brain tumor.

When tested in mice, the cell-filled chambers worked as a vaccine, protecting them from developing tumors after being injected with glioblastoma cells. The team's findings were published today in the journal Cancer Immunology, Immunotherapy.

One challenge in using the immune system to fight brain cancer, Hooper said, is making sure the immune cells can get into the brain, which is protected by the blood brain barrier. In this case, brain surgery itself may help.

"Surgery will do that for us," said Hooper. "The damage through the surgery will trigger mechanisms that will allow a window of opportunity for cells from the periphery to act."

Eventually, Hooper said, researchers would like to find a way to skip the surgical step. But for now, they want to test how effective their basic approach will be in patients with the best shot of benefiting from the technique -- those with healthy immune systems not yet ravaged by radiation or chemotherapy. They plan to enroll about 30 previously untreated glioblastoma patients in a phase II trial in January.