Simplifying Resect and Discard Strategies for Real-Time Assessment of Diminutive Colorectal Polyps

Measuring Size of Colorectal Polyps Using a Virtual Scale Endoscope or Visual Assessment: A Randomized Controlled Trial

INTRODUCTION

This study aimed to compare the accuracy of polyp size measurements using a virtual scale endoscope (VSE) with an integrated laser-based adaptive scale function and visual assessment (VA) during colonoscopies.

METHODS

We conducted a single-blinded, prospective randomized controlled trial. Eligible patients (aged 45-80 years) undergoing screening, surveillance, or diagnostic colonoscopies were randomly assigned (1:1) into 2 groups. In the intervention group, all detected polyps were measured for size using VSE; in the control group, all polyps were measured using VA. Size measurements were compared with a reference standard of digital caliper measurement immediately post polypectomy. The primary outcome was the relative accuracy of real-time VSE measurement compared with VA. Secondary outcomes included the mean differences and the correlations between VSE or VA sizes and the reference standard of measurement.

RESULTS

Overall, 230 patients were enrolled and randomized. The relative size measurement accuracy of VSE was 84% in 118 polyps, which was significantly higher than that of VA (105 polyps; 68.4%, P < 0.001). VSE resulted in a significantly higher percentage of size measurements within 25% of true size compared with VA (81.4% vs 41%, P < 0.001). VSE had a significantly lower percentage for >5-mm polyps incorrectly sized as 1-5 mm compared with VA (13.5% vs 57.1%; P < 0.001) and a significantly lower percentage for >3-mm polyps incorrectly sized as 1-3 mm compared with VA (11.3% vs 56.5%; P < 0.001).

DISCUSSION

VSE significantly improves the size measurement accuracy of colorectal polyps during colonoscopies compared with VA and results in fewer misclassifications at relevant decision-making size thresholds.

Colon polyps: updates in classification and management

PURPOSE OF REVIEW

Colon polyps are potential precursors to colorectal cancer (CRC), which remains one of the most common causes of cancer-associated death. The proper identification and management of these colorectal polyps is an important quality measure for colonoscopy outcomes. Here, we review colon polyp epidemiology, their natural history, and updates in endoscopic classification and management.

RECENT FINDINGS

Colon polyps that form from not only the adenoma, but also the serrated polyp pathway have significant risk for future progression to CRC. Therefore, correct identification and management of sessile serrated lesions can improve the quality of screening colonoscopy. Malignant polyp recognition continues to be heavily reliant on well established endoscopic classification systems and plays an important role in intraprocedural management decisions. Hot snare remains the gold standard for pedunculated polyp resection. Nonpedunculated noninvasive lesions can be effectively removed by large forceps if diminutive, but cold snare is preferred for colon polyps 3-20 mm in diameter. Larger lesions at least 20 mm require endoscopic mucosal resection. Polyps with the endoscopic appearance of submucosal invasion require surgical referral or advanced endoscopic resection in select cases. Advances in artificial intelligence may revolutionize endoscopic polyp classification and improve both patient and cost-related outcomes of colonoscopy.

SUMMARY

Clinicians should be aware of the most recent updates in colon polyp classification and management to provide the best care to their patients initiating screening colonoscopy.

Application of artificial intelligence in endoscopic gastrointestinal tumors

With an increasing number of patients with gastrointestinal cancer, effective and accurate early diagnostic clinical tools are required provide better health care for patients with gastrointestinal cancer. Recent studies have shown that artificial intelligence (AI) plays an important role in the diagnosis and treatment of patients with gastrointestinal tumors, which not only improves the efficiency of early tumor screening, but also significantly improves the survival rate of patients after treatment. With the aid of efficient learning and judgment abilities of AI, endoscopists can improve the accuracy of diagnosis and treatment through endoscopy and avoid incorrect descriptions or judgments of gastrointestinal lesions. The present article provides an overview of the application status of various artificial intelligence in gastric and colorectal cancers in recent years, and the direction of future research and clinical practice is clarified from a clinical perspective to provide a comprehensive theoretical basis for AI as a promising diagnostic and therapeutic tool for gastrointestinal cancer.

The imitation game: a review of the use of artificial intelligence in colonoscopy, and endoscopists' perceptions thereof

The development of deep learning systems in artificial intelligence (AI) has enabled advances in endoscopy, and AI-aided colonoscopy has recently been ushered into clinical practice as a clinical decision-support tool. This has enabled real-time AI-aided detection of polyps with a higher sensitivity than the average endoscopist, and evidence to support its use has been promising thus far. This review article provides a summary of currently published data relating to AI-aided colonoscopy, discusses current clinical applications, and introduces ongoing research directions. We also explore endoscopists' perceptions and attitudes toward the use of this technology, and discuss factors influencing its uptake in clinical practice.

Validation of the Modified Location-based Resect-and-discard Strategy Requiring Pathology Examination of Sigmoid Diminutive Polyps

BACKGROUND AND AIMS

Recently, the location-based resect-and-discard (LBRD) strategy, which does not depend on optical diagnosis, was developed and demonstrated different surveillance interval agreement with the pathology-based reference in several researches. We aimed to evaluate the performance of LBRD in our first-time colonoscopy cohort, and improve the LBRD.

METHODS

The first-time colonoscopy with complete pathologic information were enrolled. The accuracy of LBRD strategy applied in diminutive polyps in different colonic segments was used as indicator to develop modified LBRD (mLBRD) strategy. Surveillance interval agreement with pathology-based reference was compared between LBRD and mLBRD. The ≥ 90% agreement with pathology was used as benchmark.

RESULTS

The polyps in sigmoid colon were significantly associated with higher proportion of neoplastic compared with polyps in rectum. The accuracy of LBRD applied in polyps in sigmoid colon were only 53.5%, which was significantly lower than that applied in polyps in other colonic segments. Thus, we hypothesized that mLBRD requiring pathology examination of diminutive polyps in sigmoid colon was more efficient in clinical use. The mLBRD significantly outperformed LBRD in surveillance interval agreement with pathology-based reference (90.2% vs. 83.4%, P<0.001), had lower proportion of patients assigned a longer surveillance interval (3.6% vs. 10.5%, P<0.001) and reached the benchmark, although the proportion of patients with an immediate surveillance interval recommendations and pathology examination avoided decreased.

CONCLUSIONS

The mLBRD, but not LBRD, achieved sufficient surveillance interval agreement with pathology-based surveillance interval assignment and reduced over 30% of pathology examinations.

Artificial intelligence in endoscopy: Overview, applications, and future directions

Since the emergence of artificial intelligence (AI) in medicine, endoscopy applications in gastroenterology have been at the forefront of innovations. The ever-increasing number of studies necessitates the need to organize and classify applications in a useful way. Separating AI capabilities by computer aided detection (CADe), diagnosis (CADx), and quality assessment (CADq) allows for a systematic evaluation of each application. CADe studies have shown promise in accurate detection of esophageal, gastric and colonic neoplasia as well as identifying sources of bleeding and Crohn's disease in the small bowel. While more advanced CADx applications employ optical biopsies to give further information to characterize neoplasia and grade inflammatory disease, diverse CADq applications ensure quality and increase the efficiency of procedures. Future applications show promise in advanced therapeutic modalities and integrated systems that provide multimodal capabilities. AI is set to revolutionize clinical decision making and performance of endoscopy.

Real-World Validation of a Computer-Aided Diagnosis System for Prediction of Polyp Histology in Colonoscopy: A Prospective Multicenter Study

INTRODUCTION

Computer-aided diagnosis (CADx) of polyp histology could support endoscopists in clinical decision-making. However, this has not been validated in a real-world setting.

METHODS

We performed a prospective, multicenter study comparing CADx and endoscopist predictions of polyp histology in real-time colonoscopy. Optical diagnosis based on visual inspection of polyps was made by experienced endoscopists. After this, the automated output from the CADx support tool was recorded. All imaged polyps were resected for histological assessment. Primary outcome was difference in diagnostic performance between CADx and endoscopist prediction of polyp histology. Subgroup analysis was performed for polyp size, bowel preparation, difficulty of location of the polyps, and endoscopist experience.

RESULTS

A total of 661 eligible polyps were resected in 320 patients aged ≥40 years between March 2021 and July 2022. CADx had an overall accuracy of 71.6% (95% confidence interval [CI] 68.0-75.0), compared with 75.2% (95% CI 71.7-78.4) for endoscopists ( P = 0.023). The sensitivity of CADx for neoplastic polyps was 61.8% (95% CI 56.9-66.5), compared with 70.3% (95% CI 65.7-74.7) for endoscopists ( P < 0.001). The interobserver agreement between CADx and endoscopist predictions of polyp histology was moderate (83.1% agreement, κ 0.661). When there was concordance between CADx and endoscopist predictions, the accuracy increased to 78.1%.

DISCUSSION

The overall diagnostic accuracy and sensitivity for neoplastic polyps was higher in experienced endoscopists compared with CADx predictions, with moderate interobserver agreement. Concordance in predictions increased this diagnostic accuracy. Further research is required to improve the performance of CADx and to establish its role in clinical practice.

Comparing size measurements of simulated colorectal polyp size and morphology groups when using a virtual scale endoscope or visual size estimation: Blinded randomized controlled trial

OBJECTIVES

The virtual scale endoscope (VSE) allows projection of a virtual scale onto colorectal polyps allowing real-time size measurements. We studied the relative accuracy of VSE compared to visual assessment (VA) for the measuring simulated polyps of different size and morphology groups.

METHODS

We conducted a blinded randomized controlled trial using simulated polyps within a colon model. Sixty simulated polyps were evenly distributed across four size groups (1-5, >5-9.9, 10-19.9, and ≥20 mm) and three Paris morphology groups (flat, sessile, and pedunculated). Six endoscopists performed polyp size measurements using random allocation of either VA or VSE.

RESULTS

A total of 359 measurements were completed. The relative accuracy of VSE was significantly higher when compared to VA for all size groups >5 mm (P = 0.004, P < 0.001, P < 0.001). For polyps ≤5 mm, the relative accuracy of VSE compared to VA was not significantly higher (P = 0.186). The relative accuracy of VSE was significantly higher when compared to VA for all morphology groups. VSE misclassified a lower percentage of >5 mm polyps as ≤5 mm (2.9%), ≥10 mm polyps as <10 mm (5.5%), and ≥20 mm polyps as <20 mm (21.7%) compared to VA (11.2%, 24.7%, and 52.3% respectively; P = 0.008, P < 0.001, and P = 0.003).

CONCLUSION

Virtual scale endoscope had significantly higher relative accuracies for every polyp size group or morphology type aside from diminutive. VSE enables the endoscopist to better classify polyps into correct size categories at clinically relevant size thresholds of 5, 10, and 20 mm.

The location-based resect and discard strategy for diminutive colorectal polyps: a prospective clinical study

BACKGROUND

Clinical implementation of the resect-and-discard strategy has been difficult because optical diagnosis is highly operator dependent. This prospective study aimed to evaluate a resect-and-discard strategy that is not operator dependent.

METHODS

The study evaluated a resect-and-discard strategy that uses the anatomical polyp location to classify colonic polyps into non-neoplastic or low risk neoplastic. All rectosigmoid diminutive polyps were considered hyperplastic and all polyps located proximally to the sigmoid colon were considered neoplastic. Surveillance interval assignments based on these a priori assumptions were compared with those based on actual pathology results and on optical diagnosis. The primary outcome was ≥ 90 % agreement with pathology in surveillance interval assignment.

RESULTS

1117 patients undergoing complete colonoscopy were included and 482 (43.1 %) had at least one diminutive polyp. Surveillance interval agreement between the location-based strategy and pathological findings using the 2020 US Multi-Society Task Force guideline was 97.0 % (95 % confidence interval [CI] 0.96-0.98), surpassing the ≥ 90 % benchmark. Optical diagnoses using the NICE and Sano classifications reached 89.1 % and 90.01 % agreement, respectively (P < 0.001), and were inferior to the location-based strategy. The location-based resect-and-discard strategy allowed a 69.7 % (95 %CI 0.67-0.72) reduction in pathology examinations compared with 55.3 % (95 %CI 0.52-0.58; NICE and Sano) and 41.9 % (95 %CI 0.39-0.45; WASP) with optical diagnosis.

CONCLUSION

The location-based resect-and-discard strategy achieved very high surveillance interval agreement with pathology-based surveillance interval assignment, surpassing the ≥ 90 % benchmark and outperforming optical diagnosis in surveillance interval agreement and the number of pathology examinations avoided.

Artificial intelligence-assisted colonoscopy: a narrative review of current data and clinical applications

Colonoscopy is the reference standard procedure for the prevention and diagnosis of colorectal cancer, which is a leading cause of cancer-related deaths in Singapore. Artificial intelligence systems are automated, objective and reproducible. Artificial intelligence-assisted colonoscopy has recently been introduced into clinical practice as a clinical decision support tool. This review article provides a summary of the current published data and discusses ongoing research and current clinical applications of artificial intelligence-assisted colonoscopy.

Evaluation of the polyp-based resect and discard strategy: a retrospective study

BACKGROUND

Standard colonoscopy practice requires removal and histological characterization of almost all detected small (< 10 mm) and diminutive (≤ 5 mm) colorectal polyps. This study aimed to test a simplified polyp-based resect and discard (PBRD) strategy that assigns surveillance intervals based only on size and number of small/diminutive polyps, without the need for pathology examination.

METHODS

A post hoc analysis was performed on patients enrolled in a prospective study. The primary outcome was surveillance interval agreement of the PBRD strategy with pathology-based management according to 2020 US Multi-Society Task Force guidelines. Chart analysis also evaluated clinician adherence to pathology-based recommendations. One-sided testing was performed with a null-hypothesis of 90 % agreement with pathology-based surveillance intervals and a two-sided 96.7 % confidence interval (CI) using correction for multiple testing.

RESULTS

452 patients were included in the study. Surveillance intervals assigned using the PBRD strategy were correct in 97.8 % (96.7 %CI 96.3-99.3 %) of patients compared with pathology-based management. The PBRD strategy reduced pathology examinations by 58.7 % while providing 87.8 % of patients with immediate surveillance interval recommendations on the day of colonoscopy, compared with 47.1 % when using pathology-based management. Chart analysis of surveillance interval assignments showed 63.3 % adherence to pathology-based guidelines.

CONCLUSION

The PBRD strategy surpassed the 90 % agreement with the pathology-based standard for determining surveillance interval, reduced the need for pathology examinations, and increased the proportion of patients receiving immediate surveillance interval recommendations. The PBRD strategy does not require expertise in optical diagnosis and may replace histological characterization of small and diminutive colorectal polyps.

Clinical validation of the SIMPLE classification for optical diagnosis of colorectal polyps

Background and study aims  A novel endoscopic optical diagnosis classification system (SIMPLE) has recently been developed. This study aimed to evaluate the SIMPLE classification in a clinical cohort. Patients and methods  All diminutive and small colorectal polyps found in a cohort of individuals undergoing screening, diagnostic, or surveillance colonoscopies underwent optical diagnosis using image-enhanced endoscopy (IEE) and the SIMPLE classification. The primary outcome was the agreement of surveillance intervals determined by optical diagnosis compared with pathology-based results for diminutive polyps. Secondary outcomes included the negative predictive value (NPV) for rectosigmoid adenomas, the percentage of pathology exams avoided, and the percentage of immediate surveillance interval recommendations. Analysis of optical diagnosis for polyps ≤ 10 mm was also performed. Results  399 patients (median age 62.6 years; 55.6 % female) were enrolled. For patients with at least one polyp ≤ 5 mm undergoing optical diagnosis, agreement with pathology-based surveillance intervals was 93.5 % (95 % confidence interval [CI] 91.4-95.6). The NPV for rectosigmoid adenomas was 86.7 % (95 %CI 77.5-93.2). When using optical diagnosis, pathology analysis could be avoided in 61.5 % (95 %CI 56.9-66.2) of diminutive polyps, and post-colonoscopy surveillance intervals could be given immediately to 70.9 % (95 %CI 66.5-75.4) of patients. For patients with at least one ≤ 10 mm polyp, agreement with pathology-based surveillance intervals was 92.7 % (95 %CI 89.7-95.1). NPV for rectosigmoid adenomas ≤ 10 mm was 85.1 % (95 %CI CI 76.3-91.6). Conclusions  IEE with the SIMPLE classification achieved the quality benchmark for the resect and discard strategy; however, the NPV for rectosigmoid polyps requires improvement.

Colonoscopy and artificial intelligence: Bridging the gap or a gap needing to be bridged?

Research in artificial intelligence (AI) in gastroenterology has increased over the last decade. Colonoscopy represents the most widely published field with regards to its use in gastroenterology. Most studies to date center on polyp detection and characterization, as well as real-time evaluation of adequacy of mucosal exposure for inspection. This review article discusses how advances in AI has bridged certain gaps in colonoscopy. In addition, the gaps formed with the development of AI that currently prevent its routine use in colonoscopy will be explored.

Optical diagnosis of colorectal polyps: a randomized controlled trial comparing endoscopic image-enhancing modalities

BACKGROUND AND AIMS

Optical polyp diagnosis using image-enhanced endoscopy (IEE) allows for real-time histology prediction of colorectal polyps. The aim of this study was to evaluate a recently introduced IEE modality (Optivista [OV]; Pentax Medical, Tokyo, Japan) in a randomized controlled trial.

METHODS

In a prospective cohort of subjects (ages 45-80 years) undergoing elective screening, surveillance, or diagnostic colonoscopy, all colorectal polyps between 1 and 5 mm underwent IEE assessment. Study subjects were randomized before their colonoscopy procedure to undergo optical polyp diagnosis using either OV IEE or iScan (IS) IEE. A validated IEE scale (NBI International Colorectal Endoscopic classification) was used for optical polyp diagnosis. The primary outcome was the agreement of surveillance intervals determined when using OV IEE compared with IS IEE in reference with pathology-based surveillance intervals. Secondary outcomes were the percentage of surveillance intervals that could be given on the same day as the procedure, percentage of pathology tests avoided, diagnostic performance, and negative predictive value (NPV) of optical diagnosis for rectosigmoid adenomas.

RESULTS

Four hundred ten patients were enrolled in the trial. The polyp detection rate was 58.6%, and the adenoma detection rate was 38.8%. The proportion of correct surveillance interval assignment when using OV or IS IEE was 96.5% versus 96.0% (P = .75). A total of 65.1% of patients could be given same-day surveillance intervals when using OV IEE versus 73.1% for IS IEE (P = .07). The NPV for rectosigmoid adenomas (including sessile serrated adenomas) was 97.5% when using OV IEE and 88.2% when using IS IEE. Using high-confidence optical diagnosis instead of pathology would have resulted in a 44.3% elimination of required pathology examinations for OV IEE versus 52.8% for IS IEE (P = .34).

CONCLUSIONS

Optical diagnosis using OV and IS IEE both surpassed the 90% benchmark of surveillance interval assignment, and no significant difference with regard to correct surveillance interval assignment was found. OV IEE surpassed the ≥90% NPV for rectosigmoid adenomas, whereas IS IEE did not. (Clinical trial registration number: NCT03515343.).

Rapid, High-Resolution, Label-Free, and 3-Dimensional Imaging to Differentiate Colorectal Adenomas and Non-Neoplastic Polyps With Micro-Optical Coherence Tomography

“Resect and discard” paradigm is one of the main strategies to deal with colorectal diminutive polyps after optical diagnosis. However, there are risks that unrecognized potentially malignant lesions are discarded without accurate diagnosis. The purpose of this study is to validate the potential of micro-optical coherence tomography (μOCT) to improve the diagnostic accuracy of colorectal lesions and help endoscopists make better clinical decision without additional pathology costs.

Uptake and barriers for implementation of the resect and discard strategy: an international survey

Background and study aims  Optical real-time diagnosis (= resect-and-discard strategy) is an alternative to histopathology for diminutive colorectal polyps. However, clinical adoption of this approach seems sparse. We were interested in evaluating potential clinical uptake and barriers for implementation of this approach. Methods  We conducted an international survey using the "Google forms" platform. Nine endoscopy societies distributed the survey. Survey questions measured current clinical uptake and barriers for implementing the resect-and-discard strategy , perceived cancer risk associated with diminutive polyps and potential concerns with using CT-colonography as follow-up, as well as non-resection of diminutive polyps. Results  Eight hundred and eight endoscopists participated in the survey. 84.2 % (95 % CI 81.6 %-86.7 %) of endoscopists are currently not using the resect-and-discard strategy and 59.9 % (95 % CI 56.5 %-63.2 %) do not believe that the resect-and-discard strategy is feasible for implementation in its current form. European (38.5 %) and Asian (45 %) endoscopists had the highest rates of resect-and-discard practice, while Canadian (13.8 %) and American (5.1 %) endoscopists had some of the lowest implementation rates. 80.3 % (95 % CI 77.5 %-83.0 %) of endoscopists believe that using the resect-and-discard strategy for diminutive polyps will not increase cancer risk. 48.4 % (95 % CI 45.0 %-51.9 %) of endoscopists believe that leaving diminutive polyps in place is associated with increased cancer risk. This proportion was slightly higher (54.7 %; 95 % CI 53.6 %-60.4 %) when asked if current CT-colonography screening practice might increase cancer risks. Conclusion  Clinical uptake of resect-and-discard is very low. Most endoscopists believe that resect-and-discard is not feasible for clinical implementation in its current form. The most important barriers for implementation are fear of making an incorrect diagnosis, assigning incorrect surveillance intervals and medico-legal consequences.

Optical diagnosis of diminutive polyps in the Dutch Bowel Cancer Screening Program: Are we ready to start?

Background and study aims  Implementation of optical diagnosis of diminutive polyps may potentially increase the efficacy and cost-effectiveness of colonoscopies. To adopt such strategy in clinical practice, the Preservation and Incorporation of Valuable endoscopic Innovations (PIVI) thresholds provide the basis to be met: ≥ 90 % negative predictive value (NPV) for diagnosis of adenomatous histology and ≥ 90 % agreement on surveillance intervals. We evaluated this within the Dutch Bowel Cancer Screening Program (BCSP). Patients and methods  Endoscopic and histological data were collected from participants of the national bowel cancer screening program with an unfavorable fecal immunochemical test referred for colonoscopy between February 2014 and August 2015 at four endoscopy centers. The "resect and discard" scenario was studied, resecting diminutive polyps without histological evaluation. Agreement between optical diagnosis and histological diagnosis was measured for surveillance intervals according to Dutch, European and American post-polypectomy surveillance guideline. Results  Fifteen certified endoscopists participated in this study and included 3028 diminutive polyps. In 2,330 patients both optical and histological diagnosis were available. Optical diagnosis of diminutive polyps showed NPV of 84 % (95 % CI 80-87) for adenomatous histology in the rectosigmoid. Applying the 'resect and discard' strategy resulted in 90.6 %, 91.2 %, 90.9 % agreement on surveillance intervals for the Dutch, European and American guideline respectively. Conclusion  Our data representing current clinical practice in the Dutch BCSP practice on optical diagnosis of diminutive polyps showed that accuracy of predicting histology remains challenging, and risk of incorrect optical diagnosis is still significant. Therefore, it is too early to safely implement these strategies.

British Society of Gastroenterology/Association of Coloproctology of Great Britain and Ireland/Public Health England post-polypectomy and post-colorectal cancer resection surveillance guidelines

These consensus guidelines were jointly commissioned by the British Society of Gastroenterology (BSG), the Association of Coloproctology of Great Britain and Ireland (ACPGBI) and Public Health England (PHE). They provide an evidence-based framework for the use of surveillance colonoscopy and non-colonoscopic colorectal imaging in people aged 18 years and over. They are the first guidelines that take into account the introduction of national bowel cancer screening. For the first time, they also incorporate surveillance of patients following resection of either adenomatous or serrated polyps and also post-colorectal cancer resection. They are primarily aimed at healthcare professionals, and aim to address:Which patients should commence surveillance post-polypectomy and post-cancer resection?What is the appropriate surveillance interval?When can surveillance be stopped? two or more premalignant polyps including at least one advanced colorectal polyp (defined as a serrated polyp of at least 10 mm in size or containing any grade of dysplasia, or an adenoma of at least 10 mm in size or containing high-grade dysplasia); or five or more premalignant polyps The Appraisal of Guidelines for Research and Evaluation (AGREE II) instrument provided a methodological framework for the guidelines. The BSG's guideline development process was used, which is National Institute for Health and Care Excellence (NICE) compliant.two or more premalignant polyps including at least one advanced colorectal polyp (defined as a serrated polyp of at least 10 mm in size or containing any grade of dysplasia, or an adenoma of at least 10 mm in size or containing high-grade dysplasia); or five or more premalignant polyps The key recommendations are that the high-risk criteria for future colorectal cancer (CRC) following polypectomy comprise either:two or more premalignant polyps including at least one advanced colorectal polyp (defined as a serrated polyp of at least 10 mm in size or containing any grade of dysplasia, or an adenoma of at least 10 mm in size or containing high-grade dysplasia); or five or more premalignant polyps This cohort should undergo a one-off surveillance colonoscopy at 3 years. Post-CRC resection patients should undergo a 1 year clearance colonoscopy, then a surveillance colonoscopy after 3 more years.