Hong launched the first chemoprevention clinical trial of its kind when he and a team of researchers demonstrated that smoking impaired the ability of vitamin A and its chemical cousin, retinoids, to keep cells healthy. In the early 1990s, they demonstrated that daily doses of retinoids could stop precancerous growths in the mouth and oral cavity from turning into cancer. They proved, for the first time, that cancer could be reversed. That work has led to examining other formulas of retinoic acids and other, unrelated agents.
Current strategies of "chemoprevention" - the use of natural or synthetic substances to reduce the risk of developing cancer - are less geared toward preventing all cancer than toward preventing specific major cancers, Lippman says.
"Great clinical strides have been made in breast, colorectal and prostate cancer prevention," Lippman says. For example, he says that tamoxifen (Nolvadex) reduced breast cancer risk by 50 percent in the Breast Cancer Prevention Trial, and finasteride (Propecia, Proscar) reduced prostate cancer risk by 25 percent in the Prostate Cancer Prevention Trial.
But men and women haven't flocked to get prescriptions for either agent because, as Lippman points out, these two large-scale trials indicated that some serious side effects came along with preventive benefits. "This stand-off between agent risks and benefits has raised a major focus of cancer prevention - tailoring interventions to specific groups of people.
"Efforts to identify people at a very high cancer risk and likely to benefit from and not be harmed by particular agents will be crucial to the future of cancer prevention," Lippman says. He leads an effort at M. D. Anderson and several other cancer centers to understand prostate cancer risk and how finasteride changed this risk in the Prostate Cancer Prevention Tr
Contact: Nancy Jensen
University of Texas M. D. Anderson Cancer Center