大腸sm癌における浸潤度の臨床診断精度―各種検査法の組み合わせによる診断

Effective Combination of Conventional, Magnifying and Ultrasonographic Endoscopies in the Diagnosis of Invasion Depth of Early Colorectal Cancer

要旨　早期大腸癌の深達度診断における通常内視鏡，拡大内視鏡，超音波内視鏡の効率的な組み合わせによる診断法の確立を目的として，各検査法での肉眼型別（隆起型，表面型）の深達度診断能とその特徴を検討した．①診断不能病変はいずれの形態においても超音波内視鏡に多くみられた．②診断不能病変を含めた深達度診断能は，隆起型では通常内視鏡は全体正診率，深達度1,000μm以上診断の特異度，陽性的中率が高く，拡大内視鏡は感度が高く，超音波内視鏡はいずれも劣っていた．表面型では全体正診率は圧倒的に通常内視鏡が高く，拡大内視鏡は深達度1,000μm以上診断の特異度，陽性的中率が低く，超音波内視鏡は感度，陽性的中率が低かった．以上の結果をもとにより正確で効率の良い検査のフローチャートを作成し，これに沿って検査を進め治療を行ったと仮定すると，誤治療率は隆起型11.6％，表面型4.8％であり，いずれも通常内視鏡のみで診断した場合の誤治療率（隆起型20.9％，表面型7.1％）より低かった．

　We studied the diagnostic ability and characteristics of the combination of conventional, magnifying and ultrasonographic endoscopies for protruded and superficial types of early colorectal cancers.

　The following results were obtained :

　① Diagnostic inability was mostly noted in endoscopic ultrasonography for both of the types of cancers.

　② Conventional endoscopy had high accuracy, specificity and positive predictive value especially in the protruded type lesions in which the carcinoma had invaded the submucosal layer by more than 1,000μm． Magnifying endoscopy also showed high sensitivity, but the diagnostic ability of endoscopic ultrasonography was inferior to the former two types of endoscopy.

　③ For superficial-type lesions, accuracy of conventional endoscopy, in particular, was superior to the other two endoscopic methods in diagnostic ability of invasion depth. Magnifying endoscopy had low specificity but it had positive predictive value of superficial type carcinoma in which submucosal invasion was more than 1,000μm. Endoscopic ultrasonography showed low sensitivity and low positive predictive value.

　On the basis of our result ①, ② and ③, a flowchart was established for effective combination of endoscopic examinations in order to obtain higher diagnostic ability.

　Supposing that diagnosis of invasion depth and treatment for cancer were performed according to this flowchart, the rate of false treatment would have been 11.6％ for protruded type lesions and 4.8％ for superficial type lesions. These rates of false treatment were lower than those of independent conventional endoscopic diagnosis (20.9％ and 7.1％ respectively).

　1) Department of Internal Medicine II, Kurume University School of Medicine, Kurume, Japan

　2) Division of Gastroenterology, Kurume University School of Medicine, Kurume, Japan