By Amanda Gardner
MONDAY, June 2 (HealthDay News) -- An experimental cancer vaccine is showing promise against the same general type of brain tumor diagnosed in Sen. Edward Kennedy, researchers are reporting.
The vaccine, when given with chemotherapy, more than doubled progression-free survival in patients with glioblastoma multiforme tumors. Kennedy was diagnosed last month with a malignant glioma, a class of brain tumor that includes glioblastoma, and underwent surgery Monday for the tumor.
"It's a very small study but the results are very encouraging," said Dr. Deepa Subramaniam, director of the brain tumor center at Georgetown University's Lombardi Comprehensive Cancer Center in Washington, D.C. "It's often said that big differences would be obvious even in small studies, [and] in this very small study the average length of time patients were alive and without progression of gliobastoma was 16 months. It's quite remarkable."
The study results were to be presented Monday at the annual meeting of the American Society of Clinical Oncology, in Chicago. The study was funded by the U.S. National Institutes of Health and Celldex Therapeutics, which has licensed the rights to the vaccine.
The American Cancer Society estimates that 21,810 malignant tumors of the brain or spinal cord will be diagnosed this year in the United States. Approximately 13,070 people -- 7,420 men and 5,650 women -- will die from these tumors. The cancers account for about 1.3 percent of all cancers and 2.2 percent of all cancer-related deaths in the United States.
Current therapies for glioblastoma multiforme (GBM) tumors include surgery, chemotherapy and radiation.
The experimental vaccine targets a protein called epithelial growth factor receptor variant III (EGFRvIII), and strengthens the body's immune response. The protein is produced in about half of all GBM tumors but not in normal tissue.
This phase II trial involved 23 patients with newly diagnosed glioblastoma that was EGFRvIII positive. In addition to the vaccine, all participants also received surgery and radiation as well as chemotherapy with the drug temozolomide (TMZ) either five days a month or continuously.
Median progression-free survival in these patients was 16.6 months, whereas typically, such patients would be expected to live only about 6.4 months, said Dr. John Sampson, lead author of the study and associate professor of neurosurgery at Duke University.
Not only that, when the tumors did recur they did so without producing the EGFRvIII protein. "Tumors which express [produce] the protein have a worse prognosis so the results are even more impressive," Sampson said.
Also surprising was the degree of immune response. The chemotherapy drug TMZ normally kills white blood cells but, in this case, resulted in a dramatic enhancement of these immune-system cells.
"It's completely counterintuitive," Sampson said, adding that he could only speculate at this point why this was so.
THE EGFRvIII vaccine appears even more promising than other cancer vaccines that are in various stages of development.
"Oftentimes these vaccines are not terribly specific to the driving force of the cancer, whereas this particular vaccine... is only being given to those whose tumors expressed this particular protein," Subramaniam explained.
Phase III trials for the vaccine have already begun and, if successful, may pave the way for marketing of the vaccine in two to four years, Sampson said.
The U.S. National Library of Medicine has more on gliomas.