The estimation of cancer incidence in Aichi Prefecture, Japan: use of degree of completeness of registration.

This study was conducted to estimate true incidence of the total number of cancer cases and of cancers at selected sites in the population of Aichi Prefecture, Japan, using the degree of completeness of registration (CR). Information on incidence (I), death (D), and cases first notified via death certificate (DCN) was based on the data from 1976 to 1993. Using this information, CR for each cancer site was calculated by gender and a 3-year period of diagnosis [CR = (1-PDCN l/D)/(1-PDCN), PDCN: proportion of DCN cases]. The true number of incident cases and incidence rates (estimated incidence rate: EIR) were then estimated from the number of cases observed and from CR. CR for all sites of cancer was 62-78 percent in males and 54-72 percent in females, and CR was higher in cancers with low I/D ratios than those with high I/D ratios. Annually, about 2,500-3,000 cases in each gender were unreported. The EIR of all sites was estimated at 252-280 in males and 213-207 in females compared with the incidence rates observed (observed incidence rate: OIR) as 157.0-218.6 in males and 115.3-149.2 in females. OIR was closer to the EIR for cancers with low I/D ratios than those with high I/D ratios. These values are important for planning and evaluating cancer control strategies in the population.