深達度による大腸癌の治療方針

Diagnosis of Depth of Invasion of Colorectal Cancer：Treatment Strategy Based on Depth of Invasion

要旨●深達度や病期による大腸癌の治療方針を述べる．治療前診断で深達度がTisまたはT1軽度浸潤と判断し，内視鏡的一括切除可能な場合は内視鏡的切除を行い，病理診断結果から経過観察か追加切除を選択する．根治手術では，cT3以深やcN＋のときはD3郭清を行う．pStage III大腸癌，再発リスクが高いpStage II大腸癌では，術後補助化学療法を考慮する．術前化学放射線療法は，“cT3以深またはcN＋”の下部直腸（Rb）癌が対象となる．Stage IVでは原発巣や遠隔転移巣の切除可能性次第で治療法が異なる．薬物療法のレジメン選択は多岐にわたっている．独居高齢患者の場合，薬物療法を行うにあたって患者を取り巻く状況をよく鑑み，患者や家族と十分に話し合っておく必要がある．

　This section outlines the treatment strategy for colorectal cancer based on the depth of invasion and disease stage. If the pretreatment diagnosis suggests a depth of invasion of Tis or T1a and en bloc endoscopic resection is feasible, endoscopic resection is performed. The decision for follow-up observation or additional resection is made based on the pathological findings.

　For radical surgery, D3 lymphadenectomy is performed when the disease is classified as cT3 or deeper or if lymph node involvement（cN＋）is suspected. In cases of pathological stage III（pStage III）colorectal cancer or pStage II disease with a high risk of recurrence, postoperative adjuvant chemotherapy should be considered.

　Preoperative chemoradiotherapy is recommended for lower rectal cancer that is cT3 or deeper or cN＋. For stage IV disease, treatment strategies vary depending on the resectability of the primary tumor and the presence of distant metastases. Various chemotherapy regimens are available, and selection depends on individual patient factors.

　For elderly patients living alone, treatment decisions should account for their overall health status and support system. A thorough discussion with the patient and their family is essential before initiating chemotherapy to ensure informed decision-making.