経鼻内視鏡スクリーニングにおける胃癌偽陰性の検討―任意型検診の成績から

Investigation of False-negative Cases in Gastric Cancer Screening with Transnasal Endoscopy: a Retrospective Study on Opportunistic Screening

要旨　自施設で施行した胃内視鏡検診を対象に，経口用内視鏡を使用した経口群と経鼻内視鏡（以下，経鼻）を用いた経鼻群に分けて，診断精度について比較した．胃癌発見率（経口群0.37％，経鼻群0.30％）および早期癌率（経口群86.7％，経鼻群87.5％）に有意差はなかったが，逐年検診群を対象とすると，経鼻群の粘膜内癌率（63.6％）は経口群（100％）に比べて有意に低かった．前回検査の見直しから，経鼻群の見逃しは11例中6例あり，5例は経鼻で見逃された．経鼻の偽陰性率は34.4％，前回検査で所見指摘困難であった5例を除くと18.8％となった．以上から，さらなる診断精度向上のためには経鼻の特性に基づいた検診手法の確立が必要と考えられた．

　Recently, transnasal endoscopy（TNE）for detection of gastric cancer（GC）has been often used in opportunistic screening. However, the efficacy of TNE remains unclear. In the present study, we investigated the accuracy of TNE for detection of early GC. We analyzed the results of endoscopic examinations that were performed as a part of opportunistic screening in our institution. In accordance with models of endoscopes applied to GC screening, subjects were divided into two groups, such as the group comprised of conventional transoral endoscopy（CE）and that of TNE. They showed no significant differences in the detection rate of GC（CE ; 0.37％ and TNE ; 0.30％, respectively）and in that of early GC（CE ; 86.7％ and TNE ; 87.5％, respectively）among the two groups. However, in subjects who underwent annual endoscopic screening, the detection rate of intramucosal cancer detected by TNE was significantly lower than that in CE（CE ; 100％ and TNE ; 63.6％, respectively）. The false-negative rate of TNE screening for GC was 34.4％. The rate adjusted after the exclusion of 6cases representing the normal findings in the previous endoscopy from the false-negative cases was 18.8％. Furthermore, six of 11 subjects（54.5％）who underwent annual endoscopy, were considered to be false-diagnostic cases in the annual screening. In addition, at the previous examination, five of them had been examined by TNE. Thus, further studies are needed to establish the appropriate screening method suited to the characteristics of TNE.