By Maureen Salamon
THURSDAY, March 12, 2015 (HealthDay News) -- Adding a simple tetanus shot to another vaccine treatment for a highly lethal form of brain cancer dramatically extended some patients' survival in a small new study.
Researchers from Duke Cancer Institute found that three of six patients with glioblastoma -- a brain tumor with a very poor prognosis -- lived years longer than expected after receiving a tetanus shot to enhance an immunotherapy targeting a virus in the tumor. One patient is still alive nearly nine years after the treatment.
Prior research had found that glioblastoma tumors harbor a strain of cytomegalovirus not present in surrounding brain tissue. This creates a natural target for immunotherapy -- therapy that harnesses the power of a patient's own immune system to help destroy cancer cells, researchers say.
"Because the [average] survival is 12 to 15 months in patients who receive a diagnosis of this tumor, we were quite surprised by the results of three patients who had much longer survival times," said study author Kristen Batich, a dual medical-doctoral degree student at Duke University.
Glioblastoma is what killed Sen. Edward Kennedy in 2009.
The new study was published online March 11 in the journal Nature.
About 15 percent of the 23,000 brain tumors diagnosed each year in the United States are glioblastomas, according to the U.S. National Cancer Institute. Initial symptoms of these malignant tumors include persistent headaches, double or blurred vision, vomiting or seizures.
Batich and her colleagues split 12 glioblastoma patients into two groups: six received a tetanus booster and six received a placebo (dummy) shot. The following day, all 12 patients underwent a treatment known as dendritic cell immunotherapy.
This treatment uses dendritic cells, which "train" the immune system to respond to a specific infectious agent. In this case, the Duke team extracted patients' white blood cells, coaxed the growth of dendritic cells and loaded them with an antigen (toxin) targeting the cytomegalovirus in glioblastoma tumors.
The dendritic cell vaccine was then injected back into the cancer patients. The purpose was to signal lymph nodes to search and attack the cytomegalovirus-laden tumor.
"We think the tetanus shot does a very good job of awakening the immune system and sort of puts the lymph nodes and entire immune system on alert," Batich explained. "It gives our dendritic cell vaccine a better opportunity to reach where it needs to go."
Even in the non-tetanus shot group, survival times were somewhat longer than average for glioblastoma patients. Half of those patients lived about 18.5 months from diagnosis, the researchers said.
Three of the six patients randomly selected to receive a tetanus shot plus dendritic cell therapy were alive at the time of researchers' survival analysis. One lived 4.8 years, while another lived 5.9 years, and the remaining patient continues to have no tumor growth 8.8 years after treatment.
"This is a group of patients that desperately need a new approach, and this is a clever and exciting approach," said Dr. David Baskin, director of the Peak Brain and Pituitary Tumor Center at Houston Methodist Hospital in Texas, who wasn't involved in the new study but has participated extensively in other brain tumor research.
"All of us in the field are eager to move away from standard chemotherapy ... and trying to attack some basic thing that cancer cells just can't do without, an Achilles' heel in the cancer," added Baskin, also vice chairman of the hospital's department of neurosurgery.
"So the idea of using the immune system to treat cancer conceptually makes sense," he said.
Batich said that no adverse side effects were observed in any study participants receiving the dendritic cell vaccine, tetanus shot, or both. She and her colleagues plan further analysis of the treatments in larger clinical trials.
"We can leverage a lot of safety with this type of vaccine as opposed to the typical standard of care for cancer patients, which is a program to kill all malignant cells but may do so at a cost of destroying healthy cells as well," she said. "This offers an advantage."