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
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