Excerpt from National Cancer Program, 1981: Director's Report and Annual Plan, Fy 1983-1987 Ten years ago we had few ideas on how to prevent cancer, but the data from epidemiologic studies and fundamental research on the mechanisms of carcinogenesis have provided us with a new perspective in 1981. We now appreciate that up to 80 percent of cancers may be associated with environ mental factors and lifestyle choices. Such choices include whether we smoke, when we choose to have children, and what we eat, to name a few. These studies also have given us clues for the prevention of cancer. For example, from studies on carcinogenesis we understand that cancer is a multi stage process. Some substances initiate the cancer process; they interact, most probably with dna, to produce permanent changes in the cell. But this event alone is often not enough to cause cancer. Other substances, called promoters, cannot cause cancer by themselves but act on cells made vulnerable by initiators. Not only does this model provide us with a framework to better understand cancer causation, but also it provides us with a strategy for preventing cancer by interfering with one of the stages. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.