ESD（PAEMも含めて）

Endoscopic Treatment of Early Colorectal Cancer：ESD Including Peranal Endoscopic Myectomy

要旨●早期大腸癌に対する内視鏡治療の中心は，分割EMRから一括切除が可能な内視鏡的粘膜下層剝離術（ESD）へと移行し，局所再発率の低減と精緻な病理評価により長期予後とサーベイランスの合理化に寄与している．本稿では，Tis癌に対するESDの有用性と治療困難因子，T1癌におけるESDの役割と限界を整理し，深部粘膜下層（SM）浸潤を伴う下部直腸T1b癌に対する拡大局所切除としての内視鏡的内輪筋切除術（PAEM）の位置付けを述べる．さらに，内視鏡的全層切除と縫合の概念にも触れ，肛門機能温存と根治性のバランスを考慮した治療戦略を概説する．

　Endoscopic treatment for early colorectal cancer has shifted from piecemeal endoscopic mucosal resection（EMR）to endoscopic submucosal dissection（ESD）, which enables en bloc resection of large superficial lesions. This transition has led to a marked reduction in local recurrence and has provided high-quality specimens for precise histopathological assessment. In Japan, ESD is now considered a standard endoscopic therapy for Tis lesions, particularly for large, laterally spreading tumors and lesions with suspected submucosal invasion.

　This article reviews the current role of ESD in Tis and T1 colorectal cancer, focusing on its indications, outcomes, treatment-limiting factors, and the notion of ESD being a “high-quality biopsy” to guide additional surgery based on the risk of lymph node metastasis. We then discuss peranal endoscopic myectomy（PAEM）as an extended local resection technique for lower rectal T1b malignancies with deep submucosal invasion, aiming to achieve negative vertical margins while maintaining a minimally invasive approach. Finally, we outline the concept of endoscopic full-thickness resection and endoscopic hand-suturing in the rectum as emerging options in selected high-risk or frail patients, highlighting the need to balance oncological safety with the preservation of anal function and quality of life.