A second study, out of the Netherlands, found that the GVAX vaccine stimulated a significant immune response in men with prostate cancer. Five out of six participants receiving the highest dose of vaccine showed declines in PSA (prostate-specific antigen) levels of 50 percent or more.
"This appears to be a promising approach," study lead author Saskia Santegoets of VU University Medical Center in Amsterdam, said at the news conference.
Another vaccine -- this one for prostate cancer that hasn't responded to other therapies -- also showed hope. Three of six patients who received the highest dose of the vaccine saw declines in PSA levels of more than 50 percent. The trial involved 24 patients overall.
According to lead author Dr. Lawrence Fong of the University of California, San Francisco, the vaccine works by "educating" the immune system."
And, finally, antibody directed enzyme pro-drug therapy (ADEPT) showed positive responses in 44 percent of patients with either colorectal, gastro-esophageal, breast, gallbladder, peritoneal, appendix, pancreas or cancer of unknown primary site. With ADEPT, an enzyme activates a drug that has been targeted to the tumor by an antibody, at the site of the tumor.
The U.S. National Cancer Institute has more on cancer vaccines.
SOURCES: April 15, 2008, teleconference with John Rothman, Ph.D., vice president of clinical development, Advaxis Inc., North Brunswick, N.J.: Saskia Santegoets, VU University Medical Center, Amsterdam, the Netherlands; Lawrence Fong, M.D., University of California, San Francisco; American Association for Cancer Research annual meeting, San Diego
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