Reassessing the epidemiology of lip cancer

The risk factors associated with carcinoma of the lip are reviewed with an aim toward reassessing the epidemiology of the disease. Descriptive studies show lip cancer to occur most commonly in aging white men. The geographic distribution of the disease varies widely, both nationally and internationally; recent studies show that at the national level there is not a uniformly high risk of lip cancer across the sunny states, as has been believed. Secular disease trends show a decline in both morbidity and mortality while survival rates have remained stable. The risk factors consistently associated with lip cancer are rural residence and outdoor occupation, but the latter does not apply to all outdoor workers. In addition, both actinic radiation and tobacco smoking have long been considered to be causally related to lip cancer. An extensive review of the literature, however, reveals that the studies evaluating the association between these exposure variables and the disease do not yield consistent results; in addition, many recent, well-designed studies fail to support independent causal hypotheses. We conclude that (1) any risk factors considered to be causally related to lip cancer must be congruent with the descriptive factors (geographic distribution, secular disease trends, etc.) and (2) although sunlight and smoking are highly likely risk factors, their interrelationship as well as their interaction with other factors, such as genetic predisposition, needs reassessment.