What Do Cancer Registry and Household Expenditure Data in Japan Tell Us About Variation in Tumour Burden ?

Data from the total of six Japanese Cancer Registries presently reporting to Cancer Incidence in Five Continents ‍demonstrate marked variation in relative prevalence of cancers at particular sites, despite the genetic homogeneity ‍of the Japanese population. Thus either major differences in registry procedures or local environment must be ‍playing an important role and since the variation is clearly changing with time, the former must be considered likely. ‍Over the last 25 year period, incidence rates for the esophagus have been generally increasing in Japan, except in ‍Miyagi where they have been persistently high. Stomach cancer rates are on the decrease, although the trend is not ‍so clear in Yamagata and Hiroshima, while colon and rectal cancers have both demonstrated consistent increment ‍throughout the period surveyed, with a remarkable correlation between the two sites evident on cross-registry ‍comparisons. Continued increases have also been apparent in lung, kidney, urinary bladder and prostate cancers in ‍males and in breast, endometrium and thyroid neoplasms in females. Cervical cancer, in contrast, is decreasing, ‍although a plateau may now have been reached in Miyagi. In the hepatopancreatic axis, patterns have generally ‍showed elevation followed by a recent reduction, although without correlations among liver, gallbladder and pancreas ‍rates at the cross-registry level. Common lifestyle factors may to some extent underly the increases seen in colon, ‍breast, urinary bladder and thyroid incidence rates, given the significant relations apparent for these in the latest ‍data across registries. Whether analysis of variation in dietary intake and exposure to other risk factors, for example ‍using data for household expenditure, may provide clues to explaining the variation apparent across Japan is a ‍question warranting further consideration. If so an expanded role for the cancer registry could well be envisaged. ‍