Prediction of Diminutive/Small Polyp Histology: Didactic vs. Computer-based Training

Colonoscopy is the gold standard for screening for bowel cancers and detection of pre-cursors to colorectal cancer (polyps). Early detection of polyps, allows endoscopic removal and therefore reduction in colorectal cancer. With improvements in technology endoscopists are detecting more lesions within the bowel with the majority small/diminutive <5mm (80%), however the clinical relevance of these lesions is minimal as the risk of advanced histology or cancer is <1%. The current practice involves removing these lesions and sending for histopathological assessment, incurring a significant risk to the patient, cost and is time-consuming, with very little benefit. Novel imaging techniques including Narrow-band imaging (NBI-Olympus, Japan), i-Scan Optical enhancement (OE-Pentax, Japan) and Blue-light laser imaging (BLI- Fujifilm, Japan) can help endoscopists characterise these small lesions between being neoplastic and non-neoplastic (hyperplastic). NBI involves the narrowing of bandwidths of light using a light filter. The light at this end of the spectrum is absorbed by haemoglobin (protein found within blood) therefore making blood vessels more pronounced. During the process whereby a polyp develops and later becomes neoplastic, there is an increase in blood vessels compared with normal tissue or hyperplastic polyps (benign), therefore NBI can be used to detect such lesions. I-Scan OE is an alternative imaging technique which enhances the pattern of the surface of polyps as well as the blood vessels, by manipulating dark-light borders and red, blue and green components of light. Blue laser imaging (BLI) is also new system for image-enhanced endoscopy using laser light. Blue laser imaging utilizes two monochromatic lasers (410 and 450 nm) instead of xenon light. A 410 nm laser visualizes vascular microarchitecture, similar to narrow band imaging, and a 450 nm laser provides white light by excitation.

These novel technologies have been demonstrated to be superior over standard white light endoscopy with NBI the most extensively investigated. A systematic analysis of 6 studies >500 polyps, resulted in a pooled sensitivity of 92%, spec 86%, accuracy of 89% at differentiating neoplastic from non-neoplastic lesions when using NBI. Head to head studies of NBI versus white light endoscopy (WLE) have shown NBI is better at differentiating between neoplastic and non-neoplastic lesions. Similar results have been found with i-Scan, with performances better than WLE and like NBI are similar to chromoendoscopy (a technique that involves spraying dye over bowel mucosa which is time-consuming and costly). BLI is a newer imaging platform, with the current evidence suggesting it is effective at differentiating polyps (neoplastic versus non-neoplastic) with accuracies of 95.2%, and when comparing with white light endoscopy the miss rate of adenoma was significantly lower with BLI (1.6% versus 10.0% p=0.001).

In order to characterise between neoplastic and non-neoplastic lesions, endoscopic scoring systems have been developed to assist endoscopists. Examples include NICE (NBI International Colorectal Endoscopic).

Recently Iacucci et al have developed a simplified classification system (SIMPLE- Simplified Identification Method for Polyp Labelling during the Endoscopy) for optical diagnosis of small and diminutive adenomas, SSA/Ps and hyperplastic polyps using the newly introduced OE-iSCAN system which achieved a high degree of diagnostic accuracy for small/diminutive polyp diagnosis. Furthermore, they have showed that a training module on SIMPLE classification resulted in an overall NPV of 91.3%. This user-friendly classification system can be used by experienced and non-experienced gastroenterologists on multiple endoscopy imaging platforms to differentiate neoplastic from non-neoplastic polyps. A classification system developed by Bisschops R et al recently using BLI called BASIC (BLI Adenoma Serrated International Classification). This takes into account the polyp surface, pit appearance and vessels, which has shown to have a high concordance amongst experts.

In the hands of experts using NBI-NICE classification system accuracies of 98.9%, sensitivity 98%, specificity 100%, NPV 97.7% and PPV100% were demonstrated when diagnosis was made with high confidence. Essential to the adopted use of these classifications is training for endoscopists, both experienced and those in training. There is good evidence that there is a short learning curve involved when using NBI. One study using a self-administered computer based training module, community based gastroenterologists (non-expert) were able to reach excellent NPV of >90% but fell short of other requirements (prediction of surveillance intervals). Much like NBI, the learning curve at acquiring the skills in order to differentiate between hyperplastic and adenomatous lesions using i-Scan has been investigated. An early study by Neumann et al demonstrated a rapid learning curve with 4 endoscopists without previous experience with i-scan reached an accuracy of at least 85% after reviewing 67-110 lesions (with individualised feedback) following a 1 hour teaching session on pit pattern analysis.

There have attempts at identifying the most effective training tool and method at teaching non-experts how to characterise lesions effectively. Studies have used still images of lesions, however this is limited as it does not reflect real-life practice as it does not allow views from different angles. It is thought videos simulate real-life practice as close as possible. A study using videos has demonstrated trainees were able to achieve accuracies of 90%.

More recently Rastogi's group sought to identify which training method was more effective in prediction of diminutive polyp histology amongst trainees: didactic face to face training versus computer-based self-learning. The participants were randomised to either receive didactic training in the form of a classroom training session or self-learning via computer-based material on characterisation of polyps using NBI. Trainees reviewed 40 videos of diminutive polyps with the histology being revealed and explained. Both groups were given a further 40 videos for testing. This study found those taught in the didactic group characterised polyps with higher confidence, but the overall performance was similar in the two groups. The accuracy and sensitivity were slightly better in the self-learning group (93.9% vs 85.7% p 0.01 and 95.0% vs 86.9%; p0.03 respectively) in those polyps assessed with high confidence. This study demonstrates that a computer-based training module can be as effective in didactic training, perhaps a reflection on the amount of online self-learning trainees are exposed to.

The investigators aim to recruit participants to receive either didactic face-to-face training or self-directed computer based learning, whereby participants will be taught how to characterise lesions using the NICE, BASIC and SIMPLE classification. The investigators aim to recruit trainees, novice endoscopists and experienced endoscopists to compare the different groups. Pre- and post-training assessments will be completed allowing us to examine the impact of training, which will consist of 40-60 videos (equal proportion of NBI, iScan OE and BLI) in the pre-training assessment and 40-60 videos (different set of videos but also equal proportion of NBI, iScan OE and BLI) in the post-training assessment. A follow up assessment will be completed at 6 months to assess the retention of skills and sustainability of colonic polyp characterisation using the optical diagnosis techniques. An existing library of NBI and OE-iScan videos will be used and further videos will be collected during routine colonoscopies with patients consenting for images to be used for teaching purposes.

The investigators hypothesise that following the training module there will be an improvement in performance between the pre-training and post-training assessments. The investigators also hypothesise that there will be no difference between the didactic face-to-face group and the self-training group.

This is an important study as better characterisation of small polyps may eventually lead to a 'resect and discard' strategy in the future. This involves characterising small or diminutive polyps (<10mm) as either non-neoplastic or neoplastic, resecting the lesion but not sending for histopathological analysis, which has significant cost savings. In order to do this training is essential. Whilst didactic training is attractive, it is costly and resource heavy. The option of self-directed learning is an attractive one as it can be delivered at times that suit the user, at their pace and can be delivered in greater volumes.

This study is unique as it is examining the impact of the training module on different groups of participants (novice, training and experienced endoscopists), using multiple endoscopic platforms(NBI, i-Scan OE and BLI) at a multicentre, international level. It will enable us to assess whether the training module improves performance using different imaging modalities.