Contrasting incidences along with descriptive markers in the epidemiology of melanoma.

The four volumes of "Cancer Incidences in Five Continents" provided the data for studying the geographical differences in melanoma incidence. The cancer cumulative incidence rate was used, along with other descriptive markers: sex ratio, age group distribution and sub-site distribution. The incidence of melanoma was correlated with other sites of cancer across populations for both sexes separately, showing a high correlation with ovarian cancer. The regions used for the main comparison were Miyagi Prefecture, Japan, Alberta, Canada and Norway. An answer was sought to the question as to whether or not the (basic) low incidence is mainly determined by endogenous factors while the (superimposed) high incidence arises under the influence of an environmental cause. Cohort studies and studies of migrant populations offer data which suggest that ultraviolet exposure is among the causal environmental factors. The correlation study emphasizes the importance of the endogenous factors. The observations on the behaviour of the descriptive markers are used to give an outline for further research using descriptive and analytical epidemiological methods.