Cuff-assisted versus cap-assisted colonoscopy for adenoma detection: results of a randomized study

• Abstract
• Introduction
• Methods
• Study design
• Patients
• Procedure
• Outcomes
• Sample size calculation
• Statistical analyses
• Results
• Discussion
• Conclusions
• References

Abstract

Background The adenoma detection rate (ADR) is the most important marker of colonoscopy quality. Devices to improve adenoma detection have been developed, such as the Endocuff and transparent cap. The aim of the current study was to examine whether there was a difference in ADR between Endocuff-assisted (EAC) and cap-assisted colonoscopy (CAC).

Methods A randomized prospective trial was conducted. Eligible patients included adults ≥ 18 years referred because of symptoms, surveillance, or colonoscopies as part of the Bowel Cancer Screening Programme (BCSP). The primary outcome measure was ADR. Secondary outcomes included mean number of adenomas, mean number of polyps, polyp detection rate, cecal intubation rate, and time to cecal intubation. Procedural measures, device removal rate, and adverse events were also recorded.

Results A total of 711 patients (51.1 % men; median age 63 years) were included, of whom 357 patients were randomized to EAC and 354 patients to CAC. In the intention-to-treat analysis, the ADR was similar in both groups: EAC 50.4 % (95 % confidence interval [CI] 45.1 – 55.7) vs. CAC 50.6 % (95 %CI 45.2 – 55.9). Similar results were obtained in the per-protocol analysis: EAC 51.6 % (95 %CI 46.2 – 57) vs. CAC 51.4 % (95 %CI 46 – 56.8). There were no differences between the two devices in ADR according to the mean number of adenomas and polyps per procedure, polyp detection rate, cecal intubation rate, and time to cecal intubation. Device removal rate and adverse events were also similar.

Conclusion In this randomized study, no differences in ADR were found between Endocuff- and cap-assisted colonoscopy.

Introduction

Colonoscopy is the current standard for the detection of colorectal neoplasia. Polyps can appear anywhere in the colon and are not always easy to detect, especially when they are located on the proximal side of colonic folds. It is estimated that up to 25 % of polyps may go unnoticed during a conventional colonoscopy [1]. The adenoma detection rate (ADR) is the most important marker of colonoscopy quality [2] [3]. Low ADR correlates with higher post-colonoscopy colorectal cancer rates [4]. Moreover, an inverse relationship between ADR and interval cancer rate has been described (for each 1 % increase in ADR, interval cancer decreases by 3 %) [5].

Measures to improve ADR have been developed, including devices such as the Endocuff and transparent cap ([Fig. 1]), which are attached to the tip of the colonoscope to allow better visualization of the colonic folds.

The Endocuff is a polypropylene device mounted onto the distal tip of the colonoscope. It consists of a fixed portion and a row of eight soft projections, which are pulled forward during withdrawal to hold back colonic folds. Several case series studies and randomized trials [6] [7] [8] [9] [10] have been conducted comparing Endocuff and conventional colonoscopy. In four randomized studies, a higher ADR was observed in the patients in whom the Endocuff was used (between 4 % and 16 % higher).

Cap-assisted colonoscopy is a simple technique that allows improved visualization of the proximal aspect of colonic folds by flattening the folds within the viewing field. Studies using the cap have reported mixed results with regard to ADR. In part, these results may be related to the technique adapted to examine the colon surface with the cap: standard colonoscopy partly relies on the wide viewing angle, whereas the cap diminishes this angle and so requires a circumferential movement. In addition, some studies were limited by sample size and often included a small number of participating endoscopists [11] [12] [13] [14]. In two large trials involving multiple endoscopists, cap-assisted colonoscopy did not improve adenoma detection [15] [16]. In a Cochrane meta-analysis, cap-assisted colonoscopy increased overall polyp detection; however, no conclusion could be drawn with respect to adenoma detection [17].

The aim of the current study was to examine whether there was a difference in ADR between Endocuff-assisted and cap-assisted colonoscopy.

Methods

Study design

A prospective randomized trial was conducted at a single tertiary institution (Hospital General Universitario de Elche, Elche, Spain) from May 2017 to December 2017. Colonoscopies were performed by eight expert endoscopists. All of them had previously performed more than 5000 colonoscopies. In Spain, colonoscopists perform colonoscopies as part of the Bowel Cancer Screening Programme (BCSP) as well as non-BCSP colonoscopies. The BSCP provides fecal occult blood testing (FOBT) to all people aged between 50 and 69 years. Those with a positive FOBT are offered a colonoscopy. Additional accreditation is not required to perform BCSP colonoscopies.

A learning curve for Endocuff has been reported [10]. Therefore, all colonoscopists were required to perform a minimum of 10 colonoscopies using the Endocuff and 10 using a cap prior to study commencement.

Patients were given instructions for colon cleansing following the usual protocol of our hospital. Colonoscopies were performed using adult high definition colonoscopes (CF H180, CF Q180 and CF HQ190; Olympus Iberia SAU, Barcelona, Spain). All procedures were carried out with patients under deep sedation controlled by the anesthesiologist or the endoscopist, according to the current protocol of our institution.

The protocol was submitted to the local Research Committee and the Research Ethics Committee with the key reference PI 8/2017, and was accepted. It was subsequently registered in a clinical trial database (ClinicalTrials.gov NCT03197987). All authors had access to the study data and approved the final version of the manuscript.

Patients

Eligible patients included all adults ≥ 18 years who attended an elective colonoscopy for the following reasons: clinical symptoms (diarrhea, anemia, lower gastrointestinal bleeding, abdominal pain, recent change in bowel habits), as part of a post-polypectomy/cancer surveillance or with positive FOBT as part of the BCSP. All patients provided informed consent to participate in the study. Patients were excluded if any of the following applied: pre-endoscopy suspicion of large-bowel obstruction or colonic stricture; active colitis (infectious, inflammatory or ischemic); acute diverticulitis; known inflammatory bowel disease; known polyposis syndromes; coagulopathy or on anticoagulants that had not been stopped prior to the procedure; if pregnant or attending for a therapeutic procedure; and when the colonoscopy was performed by residents.

Using a computer-generated randomization list, patients were assigned to Endocuff-assisted colonoscopy (EAC) or cap-assisted colonoscopy (CAC). Patients, colonoscopists, and nurses were not blind to the randomization arm, but all study analyses were conducted in a blinded fashion.

Procedure

For patients randomized to the EAC group, the Endocuff ARV120 (green) device (Arc Medical Design Ltd., Leeds, UK) was attached to the tip of the colonoscope. For patients randomized to the CAC group, a transparent cap (disposable distal attachment, model D-201 – 14304; Olympus Iberia SAU, Barcelona, Spain) was attached to the tip of the colonoscope.

Removal of the Endocuff or cap during colonoscopy was indicated in the following situations: when acute angulation in a fixed sigmoid colon rendered scope insertion more difficult; when a new diagnosis of polyposis syndrome or active colitis was made; or when a new stricture that might impede insertion was identified.

Apart from the Endocuff or cap, all colonoscopies were performed per standard of care. The colonoscopy was initiated with the patient in the left lateral position, and the colonoscope was introduced until it reached the cecal pole. Auxiliary maneuvers (abdominal pressure, changing the patient’s position, increasing stiffness of the endoscope) were used as appropriate.

Intubation of the ileum was not routinely pursued. We used a timer integrated into the processor of the computer, which was activated at the time of insertion of the colonoscope and stopped when the removal of the colonoscope was complete.

The size of detected polyps was estimated by using standard biopsy forceps or snare catheter sizes. The anatomic location of each polyp was documented, and the polyp was resected based on endoscopist preference. The distal colon was defined as the splenic flexure, descending colon, and sigmoid. The proximal colon was defined as the cecum, ascending colon, and hepatic flexure.

Endoscopists were asked to rate the quality of colonoscopy preparation as “excellent,” “good,” “fair,” or “poor/inadequate)”, according to the Aronchick scale. This was the scale used in our endoscopy unit at the time of the study. Endoscopists were also asked to assess whether the devices made it difficult or easier to resect polyps, on an ordinal scale (difficult, neutral, easier). They were also asked to record whether they had observed mucosal scratches or any complications during or immediately after the colonoscopy.

Patients were followed up for 30 days. One independent clinician reviewed each medical history to determine adverse events. Patient and procedural data were collected on case report forms during and immediately following the colonoscopy.

Outcomes

The primary outcome was ADR, defined as the proportion of patients with at least one adenoma. Secondary outcomes included mean number of adenomas per procedure (MAP) and mean number of polyps per procedure, polyp detection rate (defined as the proportion of patients with at least one polyp), cecal intubation rate, and time to cecal intubation. The distribution of polyps in the colon, detection of sessile serrated polyps, withdrawal time, ease of resecting polyps, rate of Endocuff or cap removal, and complications were also recorded for both groups.

Sample size calculation

The study was powered to demonstrate a difference in ADR between the EAC and CAC groups. Based on previous studies in which the cap [18] [19] and Endocuff [8] [10] [11] were used in patients with a variety of indications, we estimated an ADR of 30 % for the CAC group and 40 % for the EAC group. To demonstrate a 10 % increase with a 5 % significance level and 80 % power using a two-sided test, 712 patients were required.

Statistical analyses

Descriptive statistics were used for the demographic characteristics with absolute and relative frequencies. For primary and secondary outcomes, proportions were compared using the chi-squared test or the Fisher’s exact test as appropriate. The Kolmogorov-Smirnov test was applied to the continuous variables and verified that none of them followed a normal distribution; therefore, all of them were analyzed using the non-parametric Mann-Whitney U test. Proportions and continuous variables are presented as point estimates with their respective 95 % confidence intervals (CIs). All analyses were performed on an intention-to-treat (ITT) basis. Per-protocol analyses were used as sensitivity analyses for the primary outcome. No adjustments for multiple testing were made, as all of the presented analyses were considered exploratory. All tests were two-sided, and P values of < 0.05 were considered statistically significant.

The calculations were made using the statistical package PSPP 1.0.1 (GNU project-free software foundation) and EPIDAT 4.2 (Dirección Xeral Saúde Pública (Xunta de Galicia).

Results

A total of 1057 patients attended the Endoscopy Unit during the study period, 346 of whom did not meet the inclusion criteria ([Fig. 2]). Finally, 711 patients were included, of whom 357 were randomized to the EAC group and 354 to the CAC group. In 24 patients it was necessary to remove the Endocuff or cap from the tip of the endoscope. No patients missed the follow-up procedure.

Baseline patient characteristics were comparable between the groups in terms of demographic data, medical/surgical history, indication of colonoscopy, type of colonoscope used, quality of colon preparation, and prevalence of diverticula ([Table 1]).

In the ITT analysis, the ADR was similar in both groups: EAC 50.4 % vs. CAC 50.6 % (95 %CI 45.1 – 55.7 vs. 45.2 – 55.9, respectively). Similar results were obtained in the per-protocol analysis: EAC 51.6 % vs. CAC 51.4 % (95 %CI 46.2 – 57 vs. 46 – 56.8, respectively) ([Table 2]). When analyzing the ADR according to indication, no significant differences were observed between EAC and CAC groups ([Table 3]).

No significant differences were observed in MAP between the EAC and CAC groups: 1.1 vs. 1.1 (95 %CI 0.9 – 1.3 vs. 0.9 – 1.3, respectively). Mean polyp per procedure was also similar for the two groups: 1.5 vs. 1.5 (95 %CI 1.3 – 1.7 vs. 1.3 – 1.7, respectively). Similarly, the overall polyp detection rate was 57.4 % for EAC vs. 60.2 % for CAC (95 %CI 52.1 – 62.6 vs. 54.9 – 65.3, respectively) ([Table 4]).

No significant differences were found when analyzing the detection of polyps according to their location, size, or morphology ([Table 4]). Similarly, no significant differences were observed regarding the histology of the polyps. A total of 7 adenocarcinomas were detected in the EAC group compared with 10 in the CAC group ([Table 4]).

The cecal intubation rate was 94.4 % for EAC vs. 95.2 % for CAC (95 %CI 91.5 – 96.5 vs. 92.4 – 97.2, respectively). Time to cecal intubation was 280 seconds for EAC vs. 270 seconds for CAC (95 %CI 264 – 300 vs. 265 – 287, respectively) ([Table 5]). Regarding the resection of polyps, endoscopists considered that the Endocuff and cap hindered polypectomy in 3.7 % vs. 0.8 % of procedures (95 %CI 2.2 – 5.7 vs. 0.2 – 2, respectively) (P  = 0.01).

The Endocuff removal rate was 4.5 % (n = 16) whereas the cap removal rate was 2.3 % (n = 8); however, the difference did not reach statistical significance (95 %CI 2.6 – 7.2 vs. 1 – 4.4, respectively). The most common reason for Endocuff removal was marked angulation in a fixed sigmoid colon (n = 9). Other reasons included stenosis (inflammatory or anastomotic) (n = 4), severe ulcerative colitis (n = 1), stenosing rectal neoplasia (n = 1), and reduced caliber colostomy (n = 1). In the CAC group, the most frequent reason for removal of the cap was marked angulation in a fixed sigmoid colon (n = 4). Other reasons included stenosing neoplasia (n = 1), acute diverticulitis (n = 1), anastomotic stenosis (n = 1), and one case in which it was necessary to intubate the ileum but this was not possible with the cap.

The laceration rate was similar with the two devices (EAC 1.7 % vs. CAC 2.3 %; 95 %CI 0.6 – 3.6 vs. 1 – 4.4, respectively). In all cases, these were slight lacerations at the sigmoid colon that did not require any treatment. The immediate adverse event was also similar between the groups (EAC 1.4 % vs. CAC 1.1 %; 95 %CI 0.5 – 3.2 vs. 0.3 – 2.9, respectively) ([Table 5]). Two post-polypectomy hemorrhages (that were treated endoscopically) and three cases of abdominal pain were observed in the EAC group. Two cases of bradycardia during sedation and two cases of abdominal pain were observed in the CAC group. 

During the 30 daysʼ follow-up, four complications were recorded: three in the EAC group (two patients were admitted due to post-polypectomy bleeding, and one patient suffering from advanced dementia died 7 days after the colonoscopy due to shock of unknown origin), and one in the CAC group (a patient on hemodialysis with colon cancer and liver metastases died due to sepsis of respiratory origin 3 weeks after colonoscopy).

Discussion

In this prospective randomized study, we compared ADR between Endocuff-assisted and cap-assisted colonoscopy. We did not compare both devices with standard colonoscopy because we found enough evidence in the literature comparing both Endocuff and cap with standard colonoscopy. Thus, several studies showed that use of the Endocuff improves the ADR compared with standard colonoscopy [8] [10] [11] [12], whereas cap studies showed heterogeneous results [14] [15] [16] [17] [18] [19] [20] [21]. The main result of our study was that there were no differences between the two devices in terms of ADR. As far as we know, no study comparing the two devices has been published. In a study presented as an abstract during the Digestive Disease Week in Chicago 2017, in which both devices were compared, the results on ADR were similar to ours (Endocuff 50 % vs. cap 53.1 %, without statistical significance) [22].

It should be noted that in our study, the ADR among BSCP and surveillance patients was high (60.9 %), similar to that reported in other studies [12] [14]. The high ADR in BCSP colonoscopy can be explained by the fact that, in our setting, the BCSP is not a true screening colonoscopy, but instead is performed in patients with a positive FOBT. We also found a high ADR in patients referred for symptom evaluation (about 40 %). This percentage is higher than that reported in other studies (about 25 %) [12] [23]. We cannot explain this discrepancy; perhaps among patients referred for symptom evaluation, rectal bleeding or overt bleeding (situations in which the ADR is high) predominated, but the specific indications were not recorded and therefore we cannot confirm this hypothesis.

ADR is the most widely used colonoscopy quality marker, but MAP is also important because high quality colonoscopy should find all adenomas, whereas ADR only requires detection of a single adenoma per patient [24] [25]. There were no differences in MAP between the Endocuff and cap in our study. Furthermore, we did not find any differences between the two devices in terms of other indicators of colonoscopy quality, such as the polyp detection rate.

The left colon, mainly the sigmoid colon, has a smaller diameter lumen and the colonic folds are more numerous with a tendency to be superimposed, unlike in the right colon where the diameter is larger and there are fewer folds. Therefore, it would be expected that these devices increase the detection of polyps in the distal colon, as it has been reported in several studies [8] [11] [12], although in other studies this finding was not confirmed [26]. In our research, we did not observe differences in the location of the polyps between the two groups, which may indicate that both devices work in the same way in different parts of the colon.

The cecal intubation rate and time to cecal intubation were similar with the two devices. In a meta-analysis, it was concluded that both the Endocuff and cap are associated with a shorter cecal intubation time and similar cecal intubation rates compared with conventional colonoscopy [27]. Conversely, withdrawal time was also similar to that described in the literature [8] [11] [12] and showed no differences between Endocuff and cap. As the cap-assisted procedure requires more rotation maneuvers to examine the folds, its use might lead to a longer withdrawal time; however, this was not the case in our study.

One of the issues in favor of the use of Endocuff is that it is said to have advantages in the resection of polyps, by stabilizing the tip of the endoscope in the colon lumen. In our study, in most cases, both devices were neutral for polypectomy, but in a small percentage of cases, it was observed that use of these devices, especially the Endocuff, made polypectomy more difficult. It is not easy to draw conclusions from this finding, given that our study was not designed to assess this parameter. Studies are needed to assess in which type of polyps these devices hinder polypectomy.

Two important aspects of these devices are that they do not have to be removed often and they are not associated with an increase in adverse effects. In our study, the Endocuff removal rate was slightly higher than the cap removal rate (4.5 % vs. 2.3 %), without reaching statistical significance. Most cases of device removal were due to marked sigmoid angulation or to fixation of the sigmoid colon. Regarding complications, we found low rates of mucosal lacerations with both devices (Endocuff 1.7 % vs. cap 2.3 %), unlike other studies, which have reported higher rates; thus, Floer et al. reported up to 7.3 % lacerations with the use of Endocuff [8], whereas Biecker et al. reported 4 % of lacerations with the Endocuff [11]. However, in these studies, an earlier-generation Endocuff device, with two rows of rigid projections, was used. Endocuff has since been improved and differs from the previous device in having only a single row of projections that are softer and 2 mm longer. This design seems to cause fewer lacerations than the previous model. In fact, in the most recent studies, the reported rates of mucosal lacerations are very low [12].

One of the factors that may affect ADR is endoscopist preference for a particular device [28]. In our study, although we did not analyze this variable, we did observe that most endoscopists had a preference for a device. Given that we did not find relevant differences in the main parameters between the two devices, it would be advisable for colonoscopists to test them in clinical practice; individuals can then decide which device they are more comfortable with. It is important to emphasize that the use of these devices does not replace an adequate colonoscopy technique.

Several limitations of the present study should be mentioned. Despite being a controlled randomized study, both the endoscopists and nurses were not blinded to the intervention, as the cuff and cap are visible on insertion. In addition, almost all endoscopists had not routinely used the Endocuff and cap prior to the study. Although endoscopists were required to perform at least 10 Endocuff and 10 cap procedures before the study, the limited prior experience may have affected the adoption of the method. In addition, almost one third of patients were excluded; this may limit the value of the study in clinical practice. A potential deficit of our study is that to calculate the sample size, we took into account ADRs from previous studies in which screening colonoscopies were included, together with symptomatic and follow-up patients. In our study we did not include true screening colonoscopies but only colonoscopies from the BCSP (performed after a positive FOBT). These colonoscopies are associated with higher ADRs than screening colonoscopies. Therefore, we should have calculated the sample size based on a higher ADR. Finally, the study was conducted at one academic medical center, and so the results may not be generalizable to general practice.

Conclusions

In summary, in this multi-endoscopist trial, we did not find any differences in ADR between Endocuff-assisted and cap-assisted colonoscopy. Either of the two devices, depending on the preference of the endoscopist, can be used safely in patients referred for colonoscopy.

Competing interests

Dr. Sola-Vera is part of the European Expert Training group on NBI, sponsored by the Olympus company.

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Corresponding author

• References

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