早期胃癌診断の現状

Current Status of Diagnosis for Early Gastric Cancer

要旨　届け出精度の高い福井県がん登録でみると，胃癌罹患数に変動はないが，年齢調整罹患率は19年間で2/3まで減少した．早期癌比率が48％に達し，特にM癌比率が2倍となったため，5年相対生存率は15年間に約10％上昇した．県内胃癌患者の1/4を診療している当院の早期癌比率は70％を超え，3,753例に達した．平均年齢は66.4歳に上昇し，症状を呈して診断されたものは半減し，任意型検診発見例が56％に達した．早期癌拾い上げ検査として内視鏡が大半となり， 2000年以降には内視鏡切除が38％に実施された．胃上部癌の比率が3倍となり，陥凹型が増加し，複合型が半減した．M癌比率が増加し，平均癌巣径が小さくなり， 組織型ではtub1が半数を超えた．このように早期癌診断能は向上しているが，生検病理診断を基準として内視鏡観察診断を評価すると，偽陰性率32％，陽性反応適中度52％であり，いまだ満足できる内容ではない．

　The age-adjusted incidence rate of gastric cancer has decreased to two-thirds over the last 19 years, but little change was observed in the number of such malignancies registered in the Fukui Cancer Registry which is regarded as the most accurate in Japan. Because the ratio of early cancers reached 48% and the mucosal-cancer ratio, in particularly doubled, the relative five-year survival rate of gastric cancer rose by about 10% in the registry. The ratio of early cancers exceeds 70% in Fukui Prefectural Hospital in which a quarter of the patients in this prefecture have been treated. The mean age rose to 66.4 years. The ratio of patients with symptoms decreased by half and patients referred from opportunistic screening reached 56%. Recently, most of the cancers were detected by endoscopy, replacing x-ray examination, and 38% of lesions were endoscopically removed after 2000. The ratio of lesions occupying the upper stomach tripled and the macroscopic depressive-type increased while the mixed type decreased by half. The ratio of mucosal cancer increased, but the average diameter decreased, and lesions with the histological type of well differentiated tubular adenocarcinoma exceeded half. However, the false negative rate was 32% and the positive predictive value was 52% when endoscopic inspective diagnosis was compared with pathologic diagnosis of biopsy specimens. We concluded that endoscopic diagnosis for early gastric cancer is not yet satisfactory, no matter how much smaller and shallower the early gastric cancers may be.