A Randomised Controlled Trial of the Prediction of Diminutive/Small Polyp Histology: a Comparison Between Didactic Training Versus Self-directed 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.