Elsevier

The Lancet Oncology

Volume 10, Issue 12, December 2009, Pages 1171-1178
The Lancet Oncology

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Optical diagnosis of small colorectal polyps at routine colonoscopy (Detect InSpect ChAracterise Resect and Discard; DISCARD trial): a prospective cohort study

https://doi.org/10.1016/S1470-2045(09)70329-8Get rights and content

Summary

Background

Accurate optical diagnosis of small (<10 mm) colorectal polyps in vivo, without formal histopathology, could make colonoscopy more efficient and cost effective. The aim of this study was to assess whether optical diagnosis of small polyps is feasible and safe in routine clinical practice.

Methods

Consecutive patients with a positive faecal occult blood test or previous adenomas undergoing surveillance at St Mark's Hospital (London, UK), from June 19, 2008, to June 16, 2009, were included in this prospective study. Four colonoscopists with different levels of experience predicted polyp histology using optical diagnosis with high-definition white light, followed by narrow-band imaging without magnification and chromoendoscopy, as required. The primary outcome was accuracy of polyp characterisation using optical diagnosis compared with histopathology, the current gold standard. Accuracy of optical diagnosis to predict the next surveillance interval was also assessed and compared with surveillance intervals predicted by current guidelines using histopathology. This study is registered with ClinicalTrials.gov, NCT00888771.

Findings

363 polyps smaller than 10 mm were detected in 130 patients, of which 278 polyps had both optical and histopathological diagnosis. By histology, 198 of these polyps were adenomas and 80 were non-neoplastic lesions (of which 62 were hyperplastic). Optical diagnosis accurately diagnosed 186 of 198 adenomas (sensitivity 0·94; 95% CI 0·90–0·97) and 55 of 62 hyperplastic polyps (specificity 0·89; 0·78–0·95), with an overall accuracy of 241 of 260 (0·93, 0·89–0·96) for polyp characterisation. Using optical diagnosis alone, 82 of 130 patients could be given a surveillance interval immediately after colonoscopy, and the same interval was found after formal histopathology in 80 patients (98%) using British guidelines and in 78 patients (95%) using US multisociety guidelines.

Interpretation

For polyps less than 10 mm in size, in-vivo optical diagnosis seems to be an acceptable strategy to assess polyp histopathology and future surveillance intervals. Dispensing with formal histopathology for most small polyps found at colonoscopy could improve the efficiency of the procedure and lead to substantial savings in time and cost.

Funding

Leigh Family Trust, London, UK.

Introduction

Colorectal cancer is the second most common cause of cancer death in developed countries and most sporadic non-hereditary cases arise from benign adenomas.1 Colonoscopy with adenoma resection is thought to reduce the risk of subsequent colorectal cancer by as much as 80%2 and is the primary screening method in the USA and in some European countries. More than 90% of polyps detected at colonoscopy are small (6–9 mm) or diminutive (≤5 mm), with most being diminutive.3, 4, 5 Around half of all small polyps are non-neoplastic;5, 6 therefore, many polypectomies are unnecessary and expose patients to added risks during colonoscopy. Currently, even small polyps that have a very small risk of harbouring cancer are sent for histology, because the number of adenomas is a good determinant of long-term risk of advanced neoplasia and allows an informed decision on future surveillance intervals.7, 8, 9 The capability to correctly diagnose a polyp during colonoscopy (optical diagnosis) would allow recto-sigmoid hyperplastic polyps to be left in situ and small adenomas to be resected and discarded without a need for formal histopathology—possibly leading to substantial savings in time and cost, and reduction in patient risk.

Conventional white-light colonoscopy has a limited accuracy (59–84%)10, 11, 12, 13, 14, 15 in differentiating neoplastic from non-neoplastic polyps. For an expert colonoscopist, application of dyes (chromoendoscopy) with optical magnification and pit-pattern recognition allows very accurate optical diagnosis (85–96%);12, 13, 14, 16, 17 however, time, cost, and the learning curve to achieve expertise are key drawbacks to this approach. Narrow-band imaging (NBI; Olympus, Japan18, 19) is a new optical imaging modality whereby short wavelength, narrow-bandwidth “blue light” is provided by the push of a button from the colonoscope head. By enhancing mucosal detail and particularly vascular structures, NBI allows assessment of microvascular density via vascular pattern intensity (VPI)20 meshed brown-capillary network.21, 22, 23 Neoplastic tissue is characterised by increased angiogenesis, and so adenomas appear darker when viewed with NBI. Microvascular assessment seems to have a short learning curve24, 25, 26 and is a practical option for optical diagnosis. In previous studies, NBI (with and without magnification) had diagnostic accuracy similar to magnified chromoendoscopy;10, 11, 12, 13, 14, 15, 26, 27, 28, 29, 30 however, only one study, done by a single expert colonoscopist,31 assessed the clinical implications of endoscopic diagnosis on surveillance intervals. DISCARD was a prospective, cohort study that aimed to assess whether diagnosis of small polyps using simple, widely available optical techniques, particularly non-magnifying NBI, is feasible and safe in routine clinical practice.

Section snippets

Patients

Consecutive patients who were referred for a surveillance colonoscopy (for adenoma follow-up, but not polyposis syndrome) or who had a positive faecal occult blood testing (FOBT), between June 19, 2008, and June 16, 2009, were eligible. Expert colonoscopists mainly examined patients who were high-risk and FOBT-positive, as a part of the national bowel-cancer screening programme, and non-experts did routine surveillance colonoscopies. All patients had a standard bowel preparation using magnesium

Results

280 patients were invited to participate in the study and 130 were included (figure 2). 363 polyps smaller than 10 mm were resected from 130 patients (≤5 mm, n=296; 6–9 mm, n=67; table 1). No completely flat or depressed lesions (Paris 0-IIb or 0-IIc) were noted. Optical diagnosis was not attempted for three polyps (all ≤5 mm) and was made with low confidence for 37 polyps, which colonoscopists electively chose to send for formal histopathology (17 hyperplastic, 16 adenoma, three destroyed by

Discussion

This prospective study suggests that optical diagnosis at colonoscopy for small colonic polyps is feasible in routine clinical practice. Overall accuracy for optical diagnosis in this study was 93% (with 6% of adenomas incorrectly diagnosed), which is similar to the overall diagnostic yield for standard histopathology. Although the colonoscopists in this study had a wide range of experience, all were confident to rely on optical diagnosis alone in a high percentage of small polyps (89%), and

References (51)

  • A Rastogi et al.

    Recognition of surface mucosal and vascular patterns of colon polyps by using narrow-band imaging: interobserver and intraobserver agreement and prediction of polyp histology

    Gastrointest Endosc

    (2009)
  • M Hirata et al.

    Magnifying endoscopy with narrow band imaging for diagnosis of colorectal tumors

    Gastrointest Endosc

    (2007)
  • FJ van den Broek et al.

    Systematic review of narrow-band imaging for the detection and differentiation of neoplastic and nonneoplastic lesions in the colon (with videos)

    Gastrointest Endosc

    (2009)
  • DK Rex

    Narrow-band imaging without optical magnification for histologic analysis of colorectal polyps

    Gastroenterology

    (2009)
  • CA Aronchick et al.

    A novel tableted purgative for colonoscopic preparation: efficacy and safety comparisons with Colyte and Fleet Phospho-Soda

    Gastrointest Endosc

    (2000)
  • E von Elm et al.

    The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement: guidelines for reporting observational studies

    Lancet

    (2007)
  • LC Seeff et al.

    How many endoscopies are performed for colorectal cancer screening? Results from CDC's survey of endoscopic capacity

    Gastroenterology

    (2004)
  • JE East et al.

    Sporadic and syndromic hyperplastic polyps and serrated adenomas of the colon: classification, molecular genetics, natural history, and clinical management

    Gastroenterol Clin North Am

    (2008)
  • DK Rex et al.

    Accuracy of pathologic interpretation of colorectal polyps by general pathologists in community practice

    Gastrointest Endosc

    (1999)
  • S Kudo et al.

    Diagnosis of colorectal tumorous lesions by magnifying endoscopy

    Gastrointest Endosc

    (1996)
  • ME Martinez et al.

    A pooled analysis of advanced colorectal neoplasia diagnoses after colonoscopic polypectomy

    Gastroenterology

    (2009)
  • KC Noshirwani et al.

    Adenoma size and number are predictive of adenoma recurrence: implications for surveillance colonoscopy

    Gastrointest Endosc

    (2000)
  • A Rastogi et al.

    Narrow-band imaging colonoscopy—a pilot feasibility study for the detection of polyps and correlation of surface patterns with polyp histologic diagnosis

    Gastrointest Endosc

    (2008)
  • B Morson

    President's address: the polyp-cancer sequence in the large bowel

    Proc R Soc Med

    (1974)
  • SJ Winawer et al.

    Prevention of colorectal cancer by colonoscopic polypectomy: the National Polyp Study Workgroup

    N Engl J Med

    (1993)
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