Reply to Mohammed & Rembacken

We would like to thank Drs. Mohammed and Rembacken for their interest in our study [1]. In their letter to the editor, Drs. Mohammed and Rembacken suggested that “the study population was enriched and does not represent the ‘all comers’ encountered in day-to-day practice.” However, when the breakdown of specific indications for colonoscopy in our study [1] is analyzed, it is comparable to that in other published studies evaluating enhanced adenoma detection technologies, and is quite representative of what is encountered in daily practice (screening 57.5 %, surveillance 23.5 %, diagnostic colonoscopy 19 %). Therefore, we believe the polyp burden in the study cohort was no higher than what would be expected in daily practice, making the 53.2 % polyp detection rate in this study quite impressive [2] [3]. Furthermore, the authors’ claim that we included in our study only a “highly selected study group” is not completely accurate considering the pilot and feasibility design of our study evaluating new endoscopic technology, and considering that the inclusion/exclusion criteria are comparable to those in other published studies in the field [2] [3] [4] [5]. Moreover, the reported mean cecal intubation time of 4.3 minutes is also similar to that in published studies evaluating comparable technologies [2] [3]. We do agree with Drs. Mohammed and Rembacken that a limitation of our feasibility study is that it does not include a control group. However, this limitation was clearly detailed within the discussion section of the manuscript where we stated “limitations include that it is nonrandomized, with no comparison with standard forward-view colonoscopy” [1]. Moreover, we did mention that “Additional human studies should be pursued that involve comparison with standard forward-viewing colonoscopy in a back-to-back tandem design.” Indeed, intermediate results of the G-EYE tandem study [6] are intriguing, and publication of final results is awaited.

When the data on terminal ileum intubation are evaluated (5 of 47 patients, 10.6 %), it is important to recognize that, as we stated in the manuscript: “Intubation of the terminal ileum was optional and at the discretion of the colonoscopist.” Thus, this represents the attempts made to intubate the ileum. All attempts at terminal ileum intubation were successful, there were no failures, and we agree this point was not well stated in the manuscript. Likewise, retroflexion in the rectum was attempted in 31 of 47 patients (66 %) and all attempts were successful. Based on these data and based on our clinical experience with the G-EYE colonoscope, we believe the balloon does not affect the maneuverability of the colonoscope’s bending portion.

Finally, regarding right-sided adenoma detection using the G-EYE balloon colonoscope, I would like to refer the authors to Pochapin et al. [7] who reported (in abstract form) the results of the tandem study focusing on adenoma detection in the right colon. The investigators reported that 33 % of the total of adenomas detected in the study were located in the ascending colon. This implies a 2-fold higher distribution rate of adenomas in the ascending colon compared to that in the published literature of approximately 16 % [8]. Moreover, 80 % of the total adenomas detected in the ascending colon were detected by the G-EYE colonoscope. The investigators concluded that the G-EYE colonoscope was able to detect substantially more adenomas in the ascending colon compared with standard forward-view colonoscopy.

• References

• 1 Gralnek IM, Suissa A, Domanov S. Safety and efficacy of a novel balloon colonoscopy: a prospective cohort study. Endoscopy 2014; 46: 883-887
• 2 Gralnek IM, Siersema PD, Halpern Z et al. Standard forward-viewing colonoscopy versus full-spectrum endoscopy: an international, multicenter, randomized, tandem colonoscopy trial. Lancet Oncol 2014; 14: 353-360
• 3 Leufkens AM, DeMarco DC, Rastogi A et al. Effect of a retrograde-viewing device on adenoma detection rate during colonoscopy: the TERRACE study. Gastrointest Endosc 2011; 73: 480-489
• 4 Gralnek IM, Segol O, Suissa A et al. A Prospective cohort study evaluating a novel colonoscopy platform featuring full-spectrum endoscopy. Endoscopy 2013; 45: 697-702
• 5 Biecker E, Floer M, Heinecke A et al. Novel Endocuff-assisted colonoscopy significantly increases the polyp detection rate. A randomized controlled trial. J Clin Gastroenterol 2015; 49: 413-418
• 6 Shpak B, Halpern Z, Kiesslich R et al. A novel balloon-colonoscope for increased polyp detection rate – intermediate results of a randomized tandem study [abstract]. United European Gastroenterol J 2013; 1: A87
• 7 Pochapin M, Gross SA, Kiesslich R et al. A novel balloon-colonoscopy increases adenoma detection in the ascending colon [abstract]. Gastrointest Endosc 2014; 79: AB547-548
• 8 Horiuchi A, Nakayama Y, Kajiyama M et al. Invasive colorectal cancer within 5 years of negative colonoscopy in a Japanese population. Colorectal Dis 2011; 14: 1090-1094