大腸T1（SM）癌に対する完全摘除生検としてのESDの可能性

Possibility of Total Excisional Biopsy for T1 Colorectal Carcinoma

要旨　完全摘除生検を前提とした大腸T1（SM）癌の術前診断では，内視鏡的完全一括摘除が可能か否かを判別する診断学が重要である．超音波内視鏡（endoscopic ultrasonography；EUS）は客観的な貫壁性の断層像が得られ，垂直断端（VM）陰性で摘除可能か否かの診断モダリティーとして有用であり，当科ではcT1b癌の診断に積極的に施行している．その結果，cT1b癌に対する内視鏡的粘膜下層剝離術（endoscopic submucosal dissection；ESD）の完全一括摘除率は92％（34/37），穿孔率5％（2/37）であった．今回の検討対象のうちVM陽性であった3例は，内視鏡的粘膜下層高度線維化の症例あるいは浸潤先進部組織型por/簇出Grade 2のいずれかの症例であった．また，「大腸癌治療ガイドライン医師用2014年版」に準じた臨床経過の検証にて，内視鏡的摘除後根治判定基準内病変では局所・転移再発例を認めなかった．以上，EUSを含めた術前診断にて完全摘除可能と診断した場合には，大腸T1（SM）癌に対する完全一括摘除生検としてのESDは容認できると考えられた．

　ER（endoscopic resection）, especially ESD（endoscopic submucosal dissection）, is a therapeutic technique but simultaneously an important diagnostic method as a total excisional biopsy. Complete resection of the lesions, including vertical margin-negative ones, is indispensable for curative treatment. Currently, among the factors in the curative treatment based on the 2014 JSCCR guidelines for the treatment of colorectal cancer, only the depth of submucosal invasion of CRC（colorectal carcinoma）can be diagnosed prior to ER or a surgical procedure. EUS（endoscopic ultrasonography）is an essential modality for the extension of ER to T1 CRC because EUS images make it possible to directly resect the submucosal layer with a negative vertical margin. Our data showed that the incidence of histopathological vertical margin-negative T1 CRC was 92％（34/37）according to ESD. There were no cases of recurrence among the patients without additional surgical resection when the lesions fulfilled the curative treatment according to the JSCCR guidelines for the Treatment of Colorectal Cancer. Concerning the ER radical criteria for T1 CRC, endoscopists have to consider whether a patient needs additional surgical resection or not. Thus, EUS can help decide whether ESD is indicated as a complete total excisional biopsy for T1 CRC. In the near future, the criteria for T1 CRC, which can be cured only by ESD, may be extended through inclusion of some molecular pathological markers instead of conventional HE specimens.