High Mortality Rate of Stomach Cancer Caused Not by High Incidence but Delays in Diagnosis in Aomori Prefecture, Japan

Background: There are substantial differences in the mortality rates of stomach cancer among the 47 prefectures in Japan, and Aomori prefecture is one of the most severely impacted. The aims of this study were to determine the incidence and mortality rates of stomach cancer in Aomori prefecture in comparison with Japan as a whole and cast light on reasons underlying variation. Methods: Data on stomach cancer cases were extracted from the Aomori Cancer Registry Database. Incidence rates for specific stages at the time of diagnosis were cited from Monitoring of Cancer Incidence in Japan, and mortality rates for stomach cancer in Aomori prefecture and the whole of Japan were obtained from Vital Statistics. Age-standardised incidence and mortality rates were calculated using the direct method. Results: The age-standardised incidence rate of stomach cancer in Aomori prefecture was higher than in the whole of Japan for males but lower for females. However, the age-standardised mortality rates were higher in Aomori prefecture in both sexes. The proportion of localised cancers was lower in Aomori prefecture than in the whole of Japan for most age groups. Conclusions: The lower rate for localised cancer suggests that higher age-standardised mortality rates are due to delays in diagnosis, despite an attendance rate for stomach cancer screening was higher in Aomori prefecture than in the whole of Japan. One plausible explanation for the failure of successful early detection might be poor quality control during screening implementation that impedes early detection.