WASHINGTON"The search for cancer prevention agents is hampered by the fact that only one biomarkerthe prostate-specific antigen (PSA)now offers a simple, noninvasive measure of the cancer process in the body," Robert W. Day, MD, PhD, said at a meeting of the Cancer Prevention Working Group, sponsored by the Cancer Research Foundation of America (CRFA). "The need for cancer biomarkers is critical, not only for their diagnostic benefits but also to provide endpoints for judging the effectiveness of any proposed chemopreventive agents."
Without such biomarkers, the endpoints for cancer prevention would take years to reach by current epidemiologic standards, said Dr. Day, president and director emeritus of the Fred Hutchinson Cancer Research Center.
Biomarkers not only diagnose individual patients, but can identify a population at risk who can then form a homogenous group for intervention. Once such biomarkers are found, a more focused investigation of chemoprevention can proceed.
Attendees at the conference also discussed several alternative approaches to research into cancer prevention.
"At present, chemoprevention is as much a matter of chance as design," said Andrew Dannenberg, MD, professor of medicine, Weill Medical College of Cornell University. "Chemopreventive agents come into the prevention field by the side door; COX-2 inhibitors, for example, came in as an extension of their approved use as anti-inflammatory agents."
Waun Ki Hong, MD, noted that "perhaps chemoprevention should be seen as therapy for the precancer, just as chemotherapy is the drug for cancer." Dr. Hong is head of the Division of Cancer Medicine, M.D. Anderson Cancer Center. "Can you eliminate the precancerous cells entirely?" he asked. "If so, cancer can be delayed or prevented. The big question is how do you measure the endpoint?"
Yet another way of looking at prevention is to think of it as treatment of intraepithelial neoplasia, said David S. Alberts, MD, associate dean for research, Arizona Cancer Center, Tucson. "Eighty percent of patients with untreated intraepithelial neoplasia develop cancer within 5 years," he noted.