内視鏡完全一括切除可能な大腸T1癌の術前診断—超音波内視鏡の有用性と限界

Pretreatment Diagnosis of Colorectal T1 Carcinomas that Can Be Completely Resected by Endoscopy: The Usefulness and Limitations of Endoscopic Ultrasonography

要旨●EUSを施行した早期大腸癌279病変では，隆起型，表面型いずれにおいてもTis・T1a癌の69.2%に比較してT1b癌の深達度正診率が87.5%と有意に高率であり（p<0.01），EUSはT1b癌を疑う病変，特に表面型病変によい適応があると言える．内視鏡的切除後SM浸潤距離を計測したT1癌120病変中，隆起型T1癌82病変の平均SM浸潤距離は3,100μmで，表面型T1癌38病変の平均SM浸潤距離の1,100μmに比較して有意に大きかった（p<0.01）．内視鏡で完全切除可能なT1癌のSM浸潤距離のカットオフ値は隆起型で3,000μm，表面型で2,000μmであった．HFUP，通常内視鏡検査の両方を行った隆起型T1癌22病変におけるSM浸潤距離3,000μm鑑別の正診率は，HFUPで86%，通常内視鏡検査では45%，とHFUPで有意に高く（p<0.01）．同様に，表面型54病変におけるSM浸潤距離2,000μm鑑別は，HFUPで86%，通常内視鏡検査では76%，とHFUPで有意に高かった（p＝0.01）．今後のT1b癌に対する内視鏡的切除の適応拡大に向けて術前のEUSの併用は必須であると考えられる．

　Of the 279 early colorectal carcinomas that underwent EUS （endoscopic ultrasonography）before treatment, the accuracy rate of invasion depth diagnosis was significantly higher in the F&D（flat and depressed）type carcinomas than in the polypoid type carcinomas（87.5% vs 69.2% ; p<0.01）. T1b carcinomas, especially F&D type, are good candidates for EUS before treatment. Of the 120 lesions of endoscopically resected T1 carcinomas subjected to the histological measurement of SM（submucosal）invasion distance, the average SM invasion distance of 82 lesions of the polypoid type T1 carcinomas was 3,100μm and that of 38 lesions of the F&D type T1 carcinomas was 1,100μm, indicating a significantly larger（p<0.01）SM invasion distance in the polypoid type. In T1 carcinomas, the cutoff value of the SM invasion distance that can be completely resected using endoscopy was 3,000μm in the polypoid type and 2,000μm in the F&D type. In the 76 T1 carcinomas that underwent both HFUP and conventional endoscopy, the accuracy rate of 3,000μm invasion distance diagnosis in the 22 polypoid-type T1 carcinomas was significantly higher with HFUP than with conventional colonoscopy（86% vs 45% ; p<0.01）. Similarly, the SM invasion distance of 2,000μm in the 54 F&D type carcinomas was significantly higher with HFUP than with conventional colonoscopy（86% vs 76% ; p＝0.01）. Preoperative combined use of EUS can be suggested as an indispensable diagnostic modality for expanding the indications of endoscopic resection for T1b carcinomas in the future.