HIGH-DEFINITION (HD) COLONOSCOPE, which

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1 Digestive Endoscopy 2015; 27 (Suppl. 1): doi: /den Screening colonoscopy: What is the most reliable modality for colorectal lesion s characterization? Advanced technology for the improvement of adenoma and polyp detection during colonoscopy Tomohiko Moriyama, 1 Toshio Uraoka, 2 Motohiro Esaki 1 and Takayuki Matsumoto 3 1 Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, 2 Department of Gastroenterology, National Hospital Organization Tokyo Medical Center, Tokyo and 3 Division of Gastroenterology, Department of Internal Medicine, School of Medicine, Iwate Medical University, Morioka, Japan Early detection and removal of adenomatous polyps reduces colorectal cancer death. However, many studies have reported that up to 20% of adenomas can be missed during colonoscopy. To improve visualization and reduce the blind spot of the colonic mucosa for an increase in the adenoma detection rate, many endoscopic techniques and technologies have been developed. The benefit of the high-definition endoscope for improving adenoma and polyp detection is marginal. Wide-angle colonoscope has failed to improve adenoma detection compared to standard colonoscopy. Although the cap-assisted colonoscope can reduce cecal intubation times, it does not seem to improve adenoma and polyp detection. The diagnostic accuracy of the colon capsule endoscope is low compared to the conventional colonoscope. Third Eye retroscope, which provides additional retrograde viewing, has revealed significant improvement in adenoma and polyp detection compared to standard colonoscopy. However, this device increases procedural times. Recently developed full-spectrum endoscopy colonoscope and extrawide-angle-view colonoscope have demonstrated a significantly lower miss rate of polyps. However, clinical trials are mandatory to determine the efficacy of these novel technologies for cancer screening. In addition, education and training for these novel techniques and technologies should seriously be considered to improve adenoma and polyp detection. Key words: colon capsule endoscopy, extra-wide-angle-view colonoscopy, full-spectrum endoscopy, high-definition colonoscopy, Third Eye retroscope INTRODUCTION COLORECTAL CANCER (CRC) is a major cause of cancer death worldwide. In Japan, over patients are diagnosed yearly as having CRC, which is the third most common cause of cancer death. 1 It is well known that adenoma can progress to CRC according to the adenomacarcinoma sequence. 2 Therefore, early detection and removal of adenomatous polyps reduces colorectal cancer death. However, many studies have shown that up to 20% of adenomas are missed during colonoscopy due to poor visualization behind the folds and the inner curve of flexures, to flat forms of polyps and to poor bowel preparation. 3 Some populationbased studies have shown that 3 8% of CRC patients underwent colonoscopy within a few years prior to CRC diagnosis. 4,5 To improve visualization and reduce the blind Corresponding: Tomohiko Moriyama, Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Maidashi 3-1-1, Higashi-ku, Fukuoka , Japan. morimori@intmed2.med.kyushu-u.ac.jp Received 20 November 2014; accepted 22 December spot of colonic mucosa and to increase adenoma detection rate (ADR) and polyp detection rate (PDR), many endoscopic techniques and technologies have been developed. It has been estimated that 10% of the colonic surface remains to be observed under the standard forward-viewing colonoscope even with good bowel preparation. 6 So far, many endoscopic techniques, such as chromoendoscopy, water-infusion technique and retroflexion technique have been reported. 7 9 However, these endoscopic techniques require additional time and skill with an increase in the risk of colonic perforation under the retroflexion technique. Furthermore, these techniques have shown only little diagnostic yield. 7 9 Recently, novel endoscopic technologies have been developed to increase ADR and PDR during white light colonoscopy. In the present review, the provisional value of such innovative technologies for the improvement of ADR and PDR is discussed. HIGH-DEFINITION COLONOSCOPE HIGH-DEFINITION (HD) COLONOSCOPE, which provides higher quality images compared to the bs_bs_banner 40

2 Digestive Endoscopy 2015; 27 (Suppl. 1): Recent advances in colonoscopy 41 standard-definition (SD) colonoscope, can detect subtle mucosal changes. However, the efficacy of the HD colonoscope in adenoma and polyp detection is controversial. Although Rastogi et al. 10 have shown that HD white-light colonoscopy could lead to an increase in PDR when compared to SD white-light colonoscopy, another study showed no beneficial effect of the HD colonoscope in detecting colonic polyps. 11 A prospective non-randomized study by Buchner et al. 12 showed that both ADR and PDR are significantly higher in HD colonoscopy than in SD colonoscopy. However, the investigators concluded that the differences in ADR and PDR were as a result of the increase in the detection of small lesions. From these results, the benefit of the HD colonoscope for increasing ADR and PDR seems to be marginal. A meta-analysis showed that the difference in ADR between HD colonoscopy and SD colonoscopy was only 3.5%. 13 WIDE-ANGLE COLONOSCOPE WIDE-ANGLE (WA) COLONOSCOPE with 170 degrees of forward-viewing angle exposes more mucosa on the proximal side of folds than a standard colonoscope with a 140- degree viewing angle. Some studies have investigated the impact of the WA colonoscope on adenoma detection. 14,15 Disappointingly, these studies have failed to show a benefit of the WA colonoscope for ADR when compared to the standard colonoscope. However, the use of the WA colonoscope was associated with a reduction in both insertion and withdrawal times. It is thus presumed that WA colonoscopy may contribute to shorter withdrawal time without decreasing ADR. CAP-ASSISTED COLONOSCOPE IN THE CAP-ASSISTED colonoscope (CAC), a transparent cap is attached to the distal tip of a colonoscope. The cap can flatten colonic folds to improve visualization behind the folds. Although several investigations have shown that CAC can reduce cecal intubation times, its efficacy in the detection of colonic adenoma and polyp is controversial Some investigators reported that CAC increased ADR and PDR compared with standard colonoscopy, 16,17 while others found no such efficacy. 18,19 In a recently published metaanalysis, a marginal improvement of PDR by the use of CAC was found with a relative ratio of However, there was no significant improvement in ADR. 20 According to the results of this analysis, CAC does not seem to markedly improve ADR and PDR. Figure 1 Colon capsule endoscope. COLON CAPSULE ENDOSCOPE ON THE BASIS of clinical experience accumulated with small bowel capsule endoscopy, the colon capsule endoscope (CCE) has been developed by Given Imaging (Yokneam, Israel). CCE is a non-invasive procedure without sedation and air-insufflation. Figure 1 shows a second-generation colon video capsule, which have two lenses in order to cover almost 360 degrees of the colonic surface. Several investigators have assessed the accuracy of CCE in a head-to-head comparison with conventional colonoscopy. Unfortunately, the diagnostic accuracy of polyps is low when compared to conventional colonoscopy. 21,22 Spada et al. 22 reported that the sensitivity and specificity of CCE for the detection of colonic polyps >6 mm was 84% and 64%, respectively. Based on these results, the European Society of Gastrointestinal Endoscopy recommends that CCE is an alternative examination to colonoscopy in nonhigh-risk individuals for CRC. 23 As conventional colonoscopy was the gold standard in these studies, the negative predictive value of conventional colonoscopy might actually have been low. Further prospective and comparative studies are required. THIRD EYE RETROSCOPE TO REFRAIN FROM missing polyps behind colonic folds, the Third Eye Retroscope (TER; Avantis Medical Systems, Sunnyvale, CA, USA) was developed. This system consists of an imaging device that is advanced through the working channel of a colonoscope retroflexed 180 degrees. TER provides an additional retrograde view behind the folds. In a prospective study, TER improved PDR by 14.8% and ADR by 16% when compared to conventional endoscopy. 24 A back-to-back study with 488 patients has shown a 23% increase in ADR with the use of TER. 25

3 42 T. Moriyama et al. Digestive Endoscopy 2015; 27 (Suppl. 1): However, this device has some limitations. Suctioning capacity of the colonoscope is disturbed when TER is in position. A TER needs to be removed from the working channel for forceps biopsy and endoscopic therapy. This is bothersome and increases the procedure time. Leufkens et al. 25 reported that withdrawal time was approximately 2 min longer in the TER group. Furthermore, TER is expensive, because this is a single-use, disposable device. FULL-SPECTRUM ENDOSCOPE RECENTLY DEVELOPED FULL Spectrum Endoscopy System colonoscope (FUSE ; EndoChoice, Alpharetta, GA, USA) has three imagers and light-emitting diode (LED) groups at the front and both sides of the flexible tip. A total of three imagers provides high-resolution, 330- degree viewing on three video monitors horizontally displayed (Fig. 2). The first study of this novel device compared a standard forward-viewing colonoscope and a FUSE colonoscope using a colonic model with simulated polyps. 26 In this prospective, non-randomized study, 85.7% of polyps were detected with the FUSE colonoscope, whereas the detection rate was 52.9% with the forward-viewing colonoscope. More recently, the result of a randomized back-toback trial with 185 subjects was reported. 27 Although the median withdrawal time was 30 s longer in the FUSE group, the FUSE colonoscope showed a significantly lower adenoma miss rate than a standard forward-viewing colonoscope (7% vs 41%). Based on these data, it can be presumed that the FUSE colonoscope improves ADR and PDR for colonoscopy. However, more studies of the efficacy and use of three monitors at one time are needed before a definite conclusion can be made. EXTRA-WIDE-ANGLE-VIEW COLONOSCOPE EXTRA-WIDE-ANGLE-VIEW COLONOSCOPE (OLYMPUS, Tokyo, Japan) has a lateral-backward ( degrees)-viewing lens in addition to a forward (140 degrees)-viewing lens at the tip of the scope (Fig. 3). View obtained from the two lenses is displayed simultaneously on a video monitor as a single image. As with the FUSE colonoscope, the extra-wide-angle-view colonoscope provides more extensive mucosal images than a conventional colonoscope without any specific techniques required. We conducted a simulated pilot study using an anatomical colorectal model with simulated polyps to assess the efficacy of this novel device. 28 In that study, the mean PDR was significantly higher with the extra-wide-angle-view colonoscope than with the standard colonoscope despite similar Figure 2 (a) Tip of the Full Spectrum Endoscopy System colonoscope (FUSE ; EndoChoice, Alpharetta, GA, USA scope. (b) Endoscopic images of the FUSE colonoscope. Figure 3 (a) Tip of the extra-wide-angle-view colonoscope showing forward-viewing and lateral-backward-viewing lenses. (b) Endoscopic image of extra-wide-angle-view colonoscope.

4 Digestive Endoscopy 2015; 27 (Suppl. 1): Recent advances in colonoscopy 43 withdrawal times (68% vs 51%; P < ). Our results suggested that an extra-wide-angle-view colonoscope represents a considerable advancement in colorectal polyp detection. A clinical trial for the efficacy of the colonoscope on ADR and PDR is under investigation. CONCLUSION DURING THE PAST 10 years, there have been advances in endoscopic technology for the improvement of ADR and PDR. Although the WA colonoscope and CCE failed to show a significant increase in ADR and PDR when compared to the standard colonoscope, preliminary trials revealed that the HD colonoscope, CAC, TER, FUSE colonoscope and extra-wide-angle-viewing colonoscope seem to be promising for improving ADR and PDR. Well-designed clinical trials are mandatory to show the benefit of these technologies for colorectal cancer screening. 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