大腸癌内視鏡治療の適応拡大—T1b癌，T2癌の治療選択の是非

Expanding the Indications for Endoscopic Treatment of Colorectal Cancer：Assessing Treatment Choices for T1b and T2 Colorectal Cancer

要旨●T1b・T2大腸癌の標準治療は，リンパ節郭清を伴う腸切除である．一方，高齢者や重篤な併存疾患を有する症例では外科手術のリスクが高く，直腸癌では手術に伴う人工肛門を含めた排便機能障害，性・排尿機能障害などにより生活の質（QOL）が大きく損なわれうる．先進施設を中心に臓器・肛門機能温存を目的とした局所治療が検討され，内視鏡的内輪筋切除（PAEM/EID）や内視鏡的全層切除（EFTR）が試みられ実行可能性・安全性が示されつつある．これらは局所制御が期待できる一方，リンパ節転移リスクは解消できない．患者・腫瘍・施設体制・術後経過観察を含めた条件を明確にしたうえで慎重に方針を決定する必要があり，今後は施設横断的な症例集積と長期成績の検証が期待される．

　Conventional treatment for T1b and T2 colorectal cancers includes radical colectomy with lymph node dissection. However, surgical risk increases in elderly patients and in those with severe comorbidities, whereas rectal surgery can markedly impair quality of life（QOL）due to bowel dysfunction following colostomy or sexual and urinary dysfunction. Accordingly, local treatment approaches that preserve organ and anal function have been explored at advanced treatment centers, where endoscopic inner-muscle resection and endoscopic full thickness resection have been evaluated, with emerging evidence supporting their feasibility and safety. Although these approaches may offer local disease control, they do not address lymph node metastasis, therefore leaving a residual risk of cancer. Careful decision-making is necessary, with clearly defined criteria encompassing patient factors, tumor characteristics, institutional resources, and postoperative surveillance strategies. Multicenter studies and validation of long-term outcomes are warranted to address these outstanding questions.