Keywords
Polyps / adenomas / ... - CRC screening - Endoscopy Lower GI Tract - Diagnosis and imaging (inc chromoendoscopy, NBI, iSCAN, FICE, CLE...) - Quality and logistical aspects - Quality management
Introduction
Optimizing the adenoma detection rate (ADR) is a major goal in colorectal cancer (CRC)
screening, because it has long been established that ADR is inversely proportional to the risk
of post-colonoscopy CRC occurrence [1]. To achieve this goal, many optimization devices have been developed, and numerous
randomized controlled trials (RCTs) have been conducted to evaluate the benefits of these
devices compared with a “standard arm,” which corresponds to date to high-definition white
light (HD-WLI) colonoscopy. The main devices are listed below and their impact on ADR is
described ([Table 1]).
Table 1 Synthesis on the impact of optimization devices on adenoma detection and adenoma miss
rates.
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ADR
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AMR
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|
ADR, adenoma detection rate; AMR, adenoma miss rate.
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Caps (Endocuff Vision, Olympus)
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↗
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↘
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|
Computer-aided colonoscopy systems
|
↗
|
↘
|
|
Contrast enhancement devices
|
|
|
↗
|
↘
|
|
|
↗
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No available data
|
|
Caps + Computer-aided colonoscopy systems
|
↗↗
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No available data
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|
Contrast enhancement devices + Computer-aided colonoscopy systems
|
↗↗
|
No available data
|
Caps
To explore colonic mucosa behind folds and thus avoid blind spots, caps can be attached at
the tip of the colonoscope. Among them, Endocuff Vision (ECV) – which has been studied in
large RCTs – has been shown to significantly increase ADR in routine colonoscopy (even in
physicians whose ADR is already high), thus suggesting the systematic use of ECV in routine
colonoscopy [2]
[3]. In contrast to the questionable impact of caps and the first generation of the
Endocuff, an approximately 10% increase in ADR has been observed with ECV, and the device has
been found to be useful in all colon locations, except for the rectum [3]. Other caps have yielded lower results when compared with ECV, which appears to be the
best of the caps developed to date, and for which the literature is abundant [4]
[5].
Computer-aided colonoscopy systems
Computer-aided colonoscopy systems
Artificial intelligence systems recently developed to outperform human vision in polyp
detection have been evaluated in many RCTs to date, with a significant increase of
approximately 5% to 10% in ADR observed in routine colonoscopy thanks to computer-aided
detection (CADe), even in non-academic units [6]
[7]
[8]
[9]
[10]. The benefit of CADe seems to be maximal in lower detectors, decreasing linearly in
higher detectors [6]. The device, therefore, can help all endoscopists to maintain a high ADR – even at the
end of an endoscopy session – and to avoid a decrease in vigilance when hunger or fatigue sets
in. However, no one could reasonably claim to maintain high vigilance throughout the entire
duration of a real-life endoscopy session. Moreover, CADe has been found to have a positive
effect on ADR regardless of endoscopist experience in colonoscopy [9]. There are no reliable data for comparing the different CADe systems, and the fact the
systems are constantly evolving due to software updates makes comparison difficult.
Contrast enhancement devices
Contrast enhancement devices
Contrast enhancement devices have also been developed by many endoscopy companies. Among
them, linked color imaging (LCI, Fujifilm) – the most promising – has been shown to have a
positive impact on ADR in numerous RCTs [11], as well as on the sessile serrated lesion (SSL) detection rate [12]. However, conflicting data on the impact on proximal adenoma and SSL miss rates, which
are strongly suspected to be implicated in post-colonoscopy CRC, mean that LCI could only have
a moderate impact or not yet be the optimization contrast enhancement device of choice [13]. Contrast enhancement devices developed by other companies – such as new-generation
narrow-band imaging (NBI, Olympus), I-scan (Pentax) or, more recently, texture and color
enhancement imaging (TXI, Olympus) – also seem to yield good results when compared with HD-WLI
colonoscopy [14]
[15]. Few studies have compared contrast enhancement devices among themselves [16]
[17]. In any case, every endoscopy unit has its own endoscope fleet from one of the
aforementioned companies and is fairly captive to this company as regards the choice of the
contrast enhancement device.
Combining the optimization devices
Combining the optimization devices
The optimization devices described above, each of which has been shown to have benefits in
terms of ADR when compared with HD-WLI colonoscopy, seem to optimize ADR in three different
ways. The first family of devices involves exposing more mucosal surface by unfolding the
mucosa, as seen with Endocuff Vision. The second family is designed to enhance operator
vigilance, thus helping every endoscopist maintain a high ADR throughout a real-life endoscopy
session, as exemplified by CADe colonoscopy. The third aims to provide better visibility of
invisible polyps by increasing the contrast between them and the normal mucosa, as achieved
with contrast enhancement devices.
Arguably, combining these three different and complementary device families would have a
synergistic effect on lesion detection. Some studies have attempted to pit them against each
other to compare their impact on ADR [18], but such competition is arguably neither useful nor reflective of the reality of an
endoscopy unit, which can use the devices in combination. Only a few studies to date have
evaluated device combinations, with some examining the CADe-contrast-enhaced system pair [19] and others the “CADe-ECV” pair [20]
[21]
[22], with the latter pair demonstrating not only a significant increase in ADR but even a
notable significant increase in advanced ADR when compared to HD-WLI alone [20].
Toward a change in practices
Toward a change in practices
In light of the above, it is arguably no longer permissible to perform screening HD-WLI
colonoscopy without the use of at least one ADR optimization device. However, optimization
devices are still not systematically used in routine practice, and their use is still not
recommended [23]
[24]. Barriers to their use undoubtedly stem from economic factors, such as the purchase of
expensive equipment by healthcare facilities (e.g., CADe) or patient reimbursement (e.g., for
the use of ECV). There are also human factors, such as endoscopist reluctance to change their
habits. To overcome these barriers, the authorities need to be convinced to cover the
additional cost of optimization devices and endoscopists need to be convinced of the benefits
and ease of their use in routine practice. To act on these two fronts (authorities and
endoscopists), new recommendations about the quality criteria for screening colonoscopy,
specifically regarding the use of optimization devices, should be issued now. We should not
wait for publication of many more RCTs about the benefits of combining the three types of
optimization devices to make these recommendations and finally use the devices in routine
practice. Furthermore, due to the diversity and complementarity of the devices, only an
impractical eight-arm RCT study comparing the different “device families” could provide an
answer. This study would become extremely complex, with numerous arms comparing various
combinations of devices, all while the best CADe systems and the best contrast enhancement
devices have yet to be determined. In the past, not so many RCTs were necessary to switch from
non-HD to HD colonoscopy and to establish recommendations, probably because changes in image
quality and definition were immediately visible to the endoscopist, and under-diagnosis with
non-HD colonoscopes was obvious [25]
[26]. In contrast, the benefit of optimization devices is not as immediately and obviously
perceptible by human vision on the day of the procedure. Nevertheless, the literature on ADR
optimization devices is already extensive enough to conclude that a “standard colonoscopy”
represents a missed opportunity for patients. Of course, because ADR is influenced by a
multitude of other factors (endoscopist education and training, bowel preparation, withdrawal
time, and other colonoscopy quality criteria), using optimization devices will not make much
sense if these quality criteria are not already fulfilled.
On the other hand, one could argue that increasing ADR is not a goal, or ask questions
about the usefulness of diminutive polyp resection in reducing CRC incidence and mortality,
and the risk of “overdiagnosis.” As a counter argument, a recent retrospective study involving
nearly 750,000 patients found that, compared with ADRs below the median of 28.3%, detection
rates at or above the median were significantly associated with a reduced risk of
post-colonoscopy CRC and related deaths [27]. And although the most relevant modalities for CRC screening are still being debated
to date [28]
[29], the objective of achieving optimal clearance of precancerous lesions in patients
screened by colonoscopy, by detecting and removing all lesions on the day of their
colonoscopy, cannot be criticized, especially in light of recommendations to reduce the
frequency of screening colonoscopy [30].
Lastly, given that a minimum ADR threshold of 25% for a screening colonoscopy meeting
quality criteria has been determined for “standard HD-WLI screening colonoscopy” [24], and that each device taken independently significantly increases ADR, the minimum
threshold should be at least 35% for “optimized screening colonoscopy: combining the
individual benefit of each optimization device.
Conclusions
To conclude, optimization devices represent a new step in screening colonoscopy, which can
work in tandem with the standard procedure following the relevant quality parameters (with an
already definite role in screening and surveillance procedures) to improve results. The
literature and data available to date on the impact of optimization devices show that standard
screening colonoscopy without any optimization devices should no longer be considered relevant
in 2024. “Optimized screening colonoscopy” with the systematic use and combination of
optimization devices will undoubtedly raise the minimum threshold of 25% required for
“standard HD-WLI screening colonoscopy.” While the use of ADR optimization devices represents
an additional step in the contribution that colonoscopy makes to CRC screening, it is
essential to improve access to and acceptance of screening programs, as there is no worse
screening colonoscopy than a colonoscopy that is not performed.
