CHICAGO, May 30 (Xinhua) -- A multicenter clinical trial of a personalized vaccine that targets glioblastoma patients has indicated improved survival rates for such patients.

The phase three clinical trial included 331 patients at over 80 sites in four countries. Siteman Cancer Center at Barnes-Jewish Hospital and Washington University School of Medicine in St. Louis recruited one of the largest groups of patients in the trial. The patients were randomized to receive standard therapy plus the personalized vaccine, called DCVax-L, or standard therapy plus a placebo.

The analysis detailed in the study shows that all 331 patients in the trial, including those who did and did not receive the vaccine, had a median survival of just over 23 months. One-hundred patients had an average overall survival of 40.5 months or more than three years, and were designated as "extended survivors."

Investigators are particularly interested in the one-hundred patients group's response to the vaccine. Since the researchers reported that almost 90 percent of all participants received the vaccine at some point, the chances that the extended survivors are getting the vaccine, rather than placebo, are high.

"The overall patient population in the trial appears to live longer than we would typically see with current standard of care, and 30 percent of the patients have lived much longer than we would expect, given the typical course of this cancer," said oncologist Jian L. Campian, one of the study's authors and a Washington University assistant professor of medicine who treats patients at Siteman Cancer Center.

In general, patients with this cancer live 15 to 17 months.

The surprising part was that the 100 "extended survivors" don't appear to have the usual characteristics associated with a good prognosis. "We are continuing to study these patients to understand why they have done so well," said Campian.

The personalized vaccine used was specific to each patient.

After surgery to remove as much of the tumor as possible, a small amount of tumor tissue is processed and then exposed to the same patient's own immune cells, called dendritic cells. Exposure to the tumor material essentially trains the dendritic cells to seek out and destroy tumor cells. These trained dendritic cells are returned to the patient as a vaccine injected in the arm.

Relatively few vaccinations are needed: the first three are weeks apart; the next three are months apart; and then patients continue with one vaccination every six months after the first year.

Campian said the vaccine had very few side effects, especially compared with standard treatment for this cancer, which includes surgery, radiation and chemotherapy. About 2 percent of participants, namely seven patients, experienced a serious adverse event such as brain swelling or seizures that may have been related to the vaccine, according to the researchers.

The study has been published May 29 in the Journal of Translational Medicine.