病理学的にみた日本人胃癌の時代的変遷

Chronological Trends of Gastric Carcinoma in Japanese from the Pathological View Point

要旨　国立がんセンター中央病院開院以来今まで施行された13,731症例を解析した．その結果，早期に発見される胃癌（T1）症例が増え，その中で高齢者の胃癌（特に分化型）が増加していた．さらに時代とともに前庭部主体であった胃癌が体中部主体に変わってきていること，また腫瘍径が小さくなっていることがわかった．これは平均余命との関連や健診の普及および診断技術の向上と大きく関連があるものと思われる．また，近年の胃癌症例では以前の胃癌と比べ低分化型が多くなっていることから，Helicobacter pylori感染との関連や食生活などの生活環境の変化が要因となっているものと思われる．以上から今後日本人の胃癌は1960年代や1970年代に多くみられたような大きくて，進行した胃癌は減少すると考えられる．しかし一時的に高齢者における分化型の胃癌が増える一方，その後は若年傾向および低分化型腺癌の増加傾向に進むものと予想される．このことを診断および治療に今後生かしていく必要があると思われる．

　We examined chronological variations of gastric carcinoma in Japanese, who underwent surgery and endoscopic resection from 1969 to 2003 in the National Cancer Center Hospital. In 1960-1970, the incidence of advanced gastric carcinoma was high, but, early stage (T1) cancer has been increasing steadily since 1980. The incidence of early stage gastric carcinoma is 70 ％, and the size of tumor is smaller than that seen previously and histlogically differentiated type adenocarcinomas have been increasing in older persons over 60 years of age. This phenomenon reflects the development of endoscopic or radiologic techniques and the numerical increase of older people.

　We compared gastric cancer in two generations by date of birth before and after 1945. In the first generation, carcinoma of the gastric antrum and histologically differentiated type was encountered at a high incidence. In the second generation, carcinoma of the gastric body, histologically poorly differentiated type and macroscopically type 4 (linitis plastica type) cancers have been increasing.

　After 1945, the life style of Japanese has changed to a European style. The social environment in each decade is quite different. The high incidence of well-differentiated type adenocarcinoma corresponds with severe intestinal metaplasia. On the other hand, the incidence of Helicobacter pylori infection in the second generation is lower than that in the first generation, as also is the incidence or distribution of intestinal metaplasia. The location of gastric cancer will move to the upper part of the gastric body including the EG-junction in younger subjects. The incidence of histologically differentiated type adenocarcinoma will also decline.