Time trends of primary liver cancer: indication of increased incidence in selected cancer registry populations.

Primary liver cancer (PLC) data from 30 selected cancer registries covering 37 populations in 18 countries were used to compare incidence rates in two periods (2-5 yr long) between 1956 and 1972. The median distance between central years of the two periods was about 8 years. Over this interval, all-ages incidence rates, standardized to world population, showed a statistically significant increase in 17 (45.9%) of the populations for males and in 10 (27.0%) for females. Corresponding figures for the 0- to 44-year age group were 4 (10.8%) for males and 7 (18.9%) for females. One statistically significant decrease was observed among the remaining populations. Over the whole set of 37 populations the median percent yearly increase was +3.7 for males and +6.7 for females (all ages) and +1.3 for males and +8.3 for females (ages 0-44 yr). The increase in PLC was most clearly identifiable in the populations of Kracow, Poland; Alberta, Canada; and Bombay, India; and in the Jewish population of Israel. Correlations between levels and/or changes of some variables (per capita income and calorie and alcohol consumption) and changes in PLC rates provided no consistent pattern of results. Changes in PLC mortality rates showed only a weak correlation with changes in PLC incidence rates, indicating the inadequacy of mortality data to describe PLC trends. Data on PLC incidence trends, as available from routine source, appeared insufficient to determine the role of diagnosis-registration changes in the observed increase and to exclude the contribution of etiologic factors.