[Estimation of trends in cancer incidence in a population-based cancer registry]

To evaluate trends in cancer incidence adjusted for completeness of registration in a population-based cancer registry, we analyzed the data of incidence and mortality in the Aichi Cancer Registry from 1979 to 1986 and recalculated age-adjusted incidence rates (AAIRs) at the lowest completeness of registration through the study period by excluding reported cases from the registration randomly. The results were as follows: 1) The AAIRs for male stomach cancer and rectal cancer in both sexes, which did not decrease or rather increased using the original incidence figures, showed a clear decrease after adjustment. 2) The AAIRs for female stomach and uterine cancers, which also showed decreases in the original incidence, showed more marked decreases. 3) The marked increases observed for the AAIRs for colon and breast cancers in the original incidence were attenuated by about 50%. 4) The AAIRs for liver and lung cancers were also affected somewhat by the adjustment for completeness of registration. 5) Trends in the AAIRs after adjusting for completeness of registration were virtually the same as those for age-adjusted mortality rates.