There is strong evidence that the interplay of environmental exposures and genetics significantly affects colorectal cancer risk, said Dr. John D. Potter, senior vice president and director of the Division of Public Health Sciences at Fred Hutchinson Cancer Research Center, last week during a speech on the NIH campus. Dr. Potter gave the 2005 Annual Advances in Cancer Prevention Lecture, part of the NCI Division of Cancer Prevention's Summer Curriculum in Cancer Prevention.
His conclusion is based on studies that have assessed environmental exposures such as folate intake, smoking, and physical activity, as well as the use of aspirin and other nonsteroidal anti-inflammatory drugs. With aspirin, for example, several studies and randomized clinical trials have shown that it can reduce the risk of precancerous polyps. However, according to work by Dr. Potter and colleagues at Fred Hutchinson, this reduction is modulated by polymorphisms in metabolizing enzymes.
Dr. Potter also discussed HNPCC, a hereditary form of colon cancer that has undergone a significant change in phenotype since its discovery in the early 1900s. Early in the century, colorectal tumors were rare in such patients, but that has slowly changed over the years. Now, the majority of HNPCC patients have colorectal tumors - a change that Dr. Potter argued is directly influenced by changes in environmental exposures, including tobacco exposure, reduced physical activity, and dietary changes.
Tribute to a Tobacco Control Crusader
More than half a century has passed since Dr. Doll undertook the first in-depth epidemiological study of smoking and lung cancer with Austin Bradford Hill. The study, first published in 1950, not only propelled his career toward five decades of tobacco-related cancer research, but also prompted him to quit smoking.
In addition to linking smoking and lung cancer, Dr. Doll also conducted research on the relationship between smoking and heart disease, and the effects of low-level ionizing radiation.
"NCI acknowledges the legacy left by Dr. Doll. The results of his groundbreaking research have saved millions of lives," said Dr. Cathy Backinger of NCI's Tobacco Control Research Branch.