食道癌に対する化学放射線療法の原発巣の効果判定―EUSを中心に

Clinical Usefulness of Endoscopic Ultrasonography for the Evaluation of the Response of Primary Esophageal Carcinoma to Chemoradiotherapy

要旨　術前補助療法（NACRT/NAC）62例，根治療法（DCRT/DRT/DCT）79例を対象として，EUSによる食道癌原発巣効果判定の有用性と問題点を検討した．EUSによる効果判定は腫瘍厚1方向計測で行い，RECISTに準じて判定した．術前補助療法例の検討で，腫瘍厚の縮小率は病理学的効果とよく相関し，内視鏡判定と比べて奏効例を抽出できていた．しかし，効果判定時期が早期に設定されていることもあり，Grade 3の判定は難しかった．根治療法例の初回効果判定時期は平均2.4か月でCR率は32％，その後は平均5.7か月までに53％がCRと判定されていた．縮小率60％以上で層構造の回復がみられる症例にCR例が多く含まれたが，その時点でCRと判定することは適切とは言えなかった．EUSによるCR判定例の再発率は低く，EUSのほうが内視鏡より厳密にCRを判定できることが明らかとなった．salvage EMR例では高周波数細径超音波プローブによる深達度診断が有用であった．

　We examined the clinical usefulness and problems of endoscopic ultrasonography（EUS）for the evaluation of response in 62 patients with primary esophageal carcinoma who received preoperative neoadjuvant therapy（chemoradiotherapy or chemotherapy）and 79 who received definitive therapy（chemoradiotherapy, radiotherapy, or chemotherapy）. Tumor thickness was measured in one direction by EUS, and tumor response was assessed according to the Response Evaluation Criteria in Solid Tumors. In patients who received preoperative neoadjuvant therapy, the tumor reduction rate correlated with the histopathological response of tumors and was superior to endoscopic evaluation for identifying patients who responded to treatment. However, because tumor response was evaluated soon after treatment, a grade 3（markedly effective）response was difficult to determine. In patients who received definitive therapy, tumor response was initially evaluated after 2.4 months on average, and the rate of complete response was 32％. At 5.7 months on average the rate of complete response was 53％. A complete response was achieved in many patients who had a reduction rate of 60％ and higher in association with restoration of the layered structure. However, it was considered inappropriate to assign a complete response at that time. The recurrence rate was low in patients who were evaluated to have had a complete response on EUS. Our results showed that EUS was more useful than endoscopy for the strict assessment of complete response. Evaluation of the depth of invasion with a high-frequency miniature ultrasound probe was useful in patients undergoing salvage endoscopic mucosal resection.