Ⅰp・Ⅰsp型大腸癌の深達度診断―治療法決定のために

Ⅰp・Ⅰsp Type Early Colorectal Cancer-Diagnosis of Depth of Invasion for Selection of Treatment Modality

要旨　早期大腸癌の深達度診断は，拡大内視鏡や超音波内視鏡の開発・実用化によりかなり精度が上がっている．しかし，隆起型，特にⅠp・Ⅰsp型病変においては，今なお表面型に比べ深達度診断に苦慮することが多い．今回，当院におけるⅠp・Ⅰsp型大腸sm癌185病変におけるリンパ節転移率・長期予後（再発率）の検討から，適切な内視鏡診断法と内視鏡切除の適応基準を各肉眼型別に検証した．まず，内視鏡的に明らかなstalkを有するⅠp型病変においては，stalk invasionを来したものや脈管侵襲・先進部低分化腺癌陽性例においてもリンパ節転移例が1例もなく（0％；0/56），また長期予後の検討においても内視鏡治療先行群は外科手術単独群とほぼ同等の予後が得られたことから，Ⅰp型早期癌は内視鏡切除を第一選択として良い病変であることが示唆された．一方，Ⅰsp型病変については，リンパ節転移率が12.0％（10/83）あり，安易な内視鏡切除は避けなければならない．また，再発率の検討から，再発を来した4例中3例がpolypectomyによる内視鏡治療を先行させた症例であること，さらに長期予後の側面からみた場合でも，内視鏡治療先行群においては，外科手術単独群に比べ有意差はないものの予後不良の傾向がみられたことなどから，明らかなsm浸潤癌と診断されるⅠsp型病変については外科切除を第一選択とするべきであると思われた．しかし，粘膜内癌，sm浸潤癌の深達度診断に迷うようなⅠsp型早期癌に限ってのみ，粘膜下局注を加えることなどの完全切除の試みを行った後に切除し，組織学的確診をもとに追加切除の必要性を決定するという方針が適用されると考えられた．

　Since the development and use of magnifying colonoscopy and endoscopic ultrasound, the accuracy rate for diagnosis of the depth of invasion of early colorectal cancers has improved. However, it is difficult to estimate endoscopically the depth of invasion of protruding lesions such as Ⅰp and Ⅰsp ones compared to those of flat lesions. The aim of our study was to investigate the presence of lymph node metastasis and long-term prognosis (recurrence rate) of 185 early colorectal cancers macroscopically diagnosed as Ⅰp and Ⅰsp which had submucosal invasion, in order to predict the ideal treatment modality. Our results demonstrated that among the Ⅰp type lesions where a stalk was clearly identified, even when the presence of stalk invasion, vascular involvement and a poorly differentiated adenocarcinoma was present, the rate of lymph node metastasis was 0%. Furthermore, when compared with cases resected surgically, after evaluating the long-term prognosis, our results demonstrated that local endoscopic resection was sufficient. Concerning Ⅰsp type lesions, the rate of lymph node metastasis was 12%, which implies that endoscopic resection is not so easy to perform, but, when long-term prognosis was evaluated a similar prognosis can be expected in both the endoscopically and surgically resected groups. In lesions where the depth of invasion is difficult to estimate endoscopically, after evaluating technical problems such as tumor size, complete endoscopic resection using submucosal saline injection can be considered as an optional treatment. We pay this because additional surgery can be performed if the histological result does not meet the criteria for complete endoscopic resection.