Tobacco use and cancer. A reappraisal.

With approximately six million users, smokeless tobacco has received considerable scrutiny as a risk factor for oral cancer. We review the relationship between smokeless tobacco use, keratosis, and oral cancer. Several features of smokeless tobacco keratosis, including the natural history, clinical presentation, and biologic behavior, differentiate it from other leukoplakias that exhibit greater malignant potential. Previous research has demonstrated that the relative risk of oral cancer with smokeless tobacco use is 4.2, about half of the risk from smoking (relative risk = 10 to 15). Mortality data from populations with sustained high-frequency smokeless tobacco use do not support the mistaken prediction of an epidemic of oral cancer with increasing smokeless tobacco use. In fact, the risks of smokeless tobacco use compare so favorably with those of smoking that smokers who switch to smokeless tobacco reduce their risks for all tobacco-related illnesses including oral cancer. Although some criticize this proposal as less than an ideal solution for the nation's smokers, full adoption of this strategy would eventually save over 400,000 lives each year.