Trends in reported adenocarcinomas of the oesophagus and gastric cardia in Japan.

Adenocarcinomas involving the oesophagus and gastric cardia are becoming more common in Western countries, but data from Japan are limited. We sought to determine whether the frequency of these cancers in Japan has increased in recent decades. Review of national cancer mortality data, national registries of oesophageal and gastric cancer cases, and records from two large cancer centres for various time periods between 1950 and 1998 did not show increased reporting of oesophageal adenocarcinomas. In contrast, both national and cancer centre data indicate an absolute increase in the number of gastric cancers involving the C-area (proximal third of the stomach). From a national registry of resected primary gastric cancer cases, those arising in the C-area as a proportion of all tumours rose by 41.8% between 1963 (12.2% of all registered cases) and 1990 (17.3%). Analysis of true cardia (<2 cm distal to oesophagus-cardia junction) early cancers from the two cancer centres showed significant increases in both absolute number and in proportion to other gastric cancers over a 36-year period. These data suggest that the frequency of cardia cancers is increasing in Japan. Lack of a parallel increase in oesophageal adenocarcinomas could be due to misclassification artefacts and/or coding preferences for gastro-oesophageal junction tumours.