Researchers conducting a clinical trial of a cell vaccine designed to fight malignant brain tumors have found a correlation between the intensity of a patent's immune response and the clinical outcome of treatment, the Los Angeles Cedars-Sinai Medical Center reported Tuesday.
The results of the clinical trials of a dendritic vaccine whichis being tested on a specific variety of brain tumors known as glioblastoma multiforme (GBM) will be released in this week's issue of Cancer Research.
According to the report, this research is believed to be the first to document a definite "immune response-patient outcome" correlation that can be credited to altering tumors during therapy.
"Fifty-three percent of patients in our study exhibited a significant vaccine-enhanced immune response," said Dr. Keith L. Black, chairman of Cedars-Sinai's Department of Neurosurgery, director of the Maxine Dunitz Neurosurgical Institute and one of the article's authors.
"Compared to non-responders or those with limited responses, the vaccine responders had significantly longer times to tumor progression and longer survival," Black said.
Christopher J. Wheeler, a research scientist at the Dunitz Institute and the article's first and corresponding author said," no other vaccine trial in cancer patients has shown the kind of progressive correlation between immune responses and clinical outcomes that we found."
Wheeler also stated that researchers investigated whether the immune response correlation was present after vaccination alone or after post-vaccination chemotherapy.
"It was evident only after post-vaccine chemotherapy. This leads us to believe that while T-cell activity may not result in net destruction of the tumor, it is fundamentally changing the tumor into one that is predominantly comprised of chemosensitive cells rather than chemoresistant cells," Wheeler added.
The research study was initiated because GBM tumors are not readily detected or attacked by the immune system. Dendritic cells are the immune system's most powerful cells that help the immune system recognize invaders.
When a tumor is surgically removed, proteins are collected, cultured and introduced to dendritic cells taken from the patient's blood.
The new cells are then injected into the patient where they are intended to recognize and destroy lingering tumor cells. Patients received three vaccinations at two-week intervals. A fourth vaccination is given six weeks later.
The Cedars-Sinai study centered on the immune responses of 32 patients enrolled in a Phase II clinical trial. Seventeen patients had a significant positive response after three vaccinations, while 15 showed no such responsiveness.
Of those enrolled in the clinical trial, 41 percent of vaccine responders, compared to seven percent of non-responders, survived at least two years. Meanwhile, the survival rate of non-responder saveraged only about 14 months.
All patients in the trial had longer time to progression and longer time of survival, on average, than patients undergoing similar treatment without vaccination.
Source:Xinhua
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