Some researchers remain skeptical. One concern is that some vaccines target naturally occurring proteins that the immune system would not normally attack. “We are asking the body to override these existing control mechanisms,” says Mark Kelley of Vanderbilt-Ingram Cancer Center in Nashville, Tenn., who was involved with the failed Canvaxin studies. This “self” immune response could cause autoimmune disease as a side effect. Kelley also worries about the fundamental complexity of vaccines, which makes it harder to achieve full medical potential than with other cancer therapies, he feels.
Schlom, who lived through a decade of negativity over monoclonal antibodies, sees much of the nay-saying as par for the course. When it comes to new medicines, “there is always a period of skepticism,” he recounts. “I have absolutely no doubt that several years from now there will be several vaccines approved for several cancer indications.”
A Cancer Vaccine’s Mystery Deaths
Proponents of cancer vaccines note that past clinical failures nonetheless have shown that the vaccines lengthened patients’ survival times. But that was not the case this past August, when Cell Genesys in South San Francisco halted a clinical trial of the prostate cancer vaccine GVAX when it discovered that more patients receiving the vaccine plus chemotherapy had died (67 deaths) as compared with those receiving chemotherapy alone (47 deaths). The reasons are under investigation, but the 408 patients in the study had the most advanced prostate cancer possible, “exactly the patient population for which [one] would not use a vaccine,” remarks Jeffrey Schlom, chief of the Laboratory of Tumor Immunology and Biology at the National Cancer Institute. An ongoing companion study of GVAX in patients with less advanced prostate cancer should help clarify this issue.
Note: This article was originally published with the title, "Confidence Booster".