炎症性腸疾患における癌化・発育進展―UC関連大腸癌の臨床的検討

Development and Progression of UC-associated Cancer Investigated from Clinical Aspects

要旨　潰瘍性大腸炎（UC）には慢性炎症を母地とした大腸癌の合併が高率にみられる．内視鏡的サーベイランスが推奨されているが，炎症粘膜を背景とするため初期病変の診断は容易でなく，形態変化，発育速度，進展様式などの実態は明らかでない．今回，当院において診療したUC合併大腸癌（UCAC），dysplasiaを対象に癌化につながる臨床的危険因子や病変を遡及できた症例を通じ，発育・進展について検討した．UCACの平均罹患年数は14年，全大腸炎型と左側大腸炎型が97.7％を占めていた．32.3％の症例に多発傾向を認めたが，病変全体の74.6％，深達度が判明している病変のMP以深浸潤例の95.7％が直腸・S状結腸に分布していた．活動期の症例が60.5％を占め，内視鏡的に緩解と判断しえた症例はなかった．遡及が可能であった病変の検討では，比較的長期間粘膜内癌でとどまっている病変があった．早期肉眼形態で浸潤性発育を示し進行した病変は，平坦・肥厚型に多く見られた．UCACの癌化，進展ともに慢性炎症が大きく関与しており，粘膜治癒を目指した治療が重要と考えられた．

　An increased risk of ulcerative colitis-associated cancer（UCAC）has been reported in patients with long-standing ulcerative colitis（UC）and cancer surveillance is recommended. Because the early detection of UCAC by colonoscopy is difficult, the natural course and the progression rate of UCAC in the early stage is still unknown. We analyzed clinical features and risk factors of 43cases（71 lesions）of UCAC/dysplasia with retrospective follow-up. The average duration of UC at cancer diagnosis was 14 years. Forty two cases of 43（97.7％）of HCAC/dysplasia were classified as extensive colitis or left-sided colitis. Fifty three lesions of 71（74.6％）were located in the rectum and sigmoid colon. Twenty six cases of 43（60.5％）were in the clinically active stage and all of the 71 lesions had severely or moderately active inflammation around them. Therefore, it was suggested that treatment strategy consider mucosal healing is essential for prevention of cancer development and progression in UC. In addition, we showed here some lesions whose endoscopic findings could be followed by colonoscopy.