Evaluation of the Death Certificate Follow-up Method for the Analysis of Survival Rate: Data from Aichi Prefecture, Japan

To evaluate the use, for studies on survival, of death certificates from population-based cancer registries in Japan, we compared 5-year survival rates by two different methods: passive, derived from death certificates, and active, using family register systems. Registered cancer cases from Aichi Prefectural Cancer Registry were used as a model. The study subjects comprised 9244 cancer patients (3830 males and 5414 females) newly diagnosed at the Aichi Cancer Center Hospital and recorded in the Aichi Prefectural Cancer Registry between 1983 and 1991. The passive follow-up method, using death certificates, identified 87-89% of deaths among the study subjects. The proportion of deaths which were not identified by the passive follow-up method did not vary greatly with age or gender, but was higher among patients in the earlier rather than the later stages of cancer. Overall, the absolute and relative effects of unregistered deaths on apparent survival rate vary with the absolute survival rate. The absolute and relative differences between the survival rates calculated by the two methods are explained more clearly when data are analyzed by cancer site. The results of the present study provide useful information for interpreting the survival rate following diagnosis of cancer estimated by the passive follow-up method, i.e. using death certificates from a population-based cancer registry.