Risk factors of lip cancer: a critical evaluation based on epidemiological comparisons.

A description is given of the occurrence of lip, skin, and intraoral cancers in Finland in the period 1953-1973 with the aim of testing certain etiologic hypotheses. In addition, data on lip cancer were correlated with those of some other types of cancer. Substantial differences with respect to various epidemiologic parameters were found between lip and skin cancers. However, there were similarities between lip cancer and cancers of the upper gastrointestinal canal and respiratory organs (especially lung cancer). Negative geographic correlation was found between the age-adjusted incidence rate of lip cancer and that of cancers of the colon and prostate. In addition, the correlation was highly negative for the median income per capita (p less than 0.001). It was concluded that, in terms of cancer etiology, lip cancer is more closely related to cancer of the oral cavity than to that of the skin. Moreover, some specific socioeconomic factors associated with a low standard of living must be considered as noteworthy risk factors of lip cancer.