Fast track — ArticlesOptical diagnosis of small colorectal polyps at routine colonoscopy (Detect InSpect ChAracterise Resect and Discard; DISCARD trial): a prospective cohort study
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)
- et al.
Polyp size and advanced histology in patients undergoing colonoscopy screening: implications for CT colonography
Gastroenterology
(2008) - et al.
Prevalence of clinically important histology in small adenomas
Clin Gastroenterol Hepatol
(2006) - et al.
Screening and surveillance for the early detection of colorectal cancer and adenomatous polyps, 2008: a joint guideline from the American Cancer Society, the US Multi-Society Task Force on colorectal cancer, and the American College of Radiology
Gastroenterology
(2008) - et al.
Five-year colon surveillance after screening colonoscopy
Gastroenterology
(2007) - et al.
Accuracy of high resolution of chromoendoscopy in prediction of histologic findings in diminutive lesions of the rectosigmoid
Gastrointest Endosc
(2006) - et al.
A comparison of magnifying and nonmagnifying colonoscopy for diagnosis of colorectal polyps: a prospective study
Gastrointest Endosc
(2003) Optical contrast endoscopy: is it ready for routine use?
Gastroenterology
(2009)- et al.
Comparison of magnified pit pattern interpretation with narrow band imaging versus chromoendoscopy for diminutive colonic polyps: a pilot study
Gastrointest Endosc
(2007) - et al.
Evaluation of microvessels in colorectal tumors by narrow band imaging magnification
Gastrointest Endosc
(2007) - et al.
Narrow-band imaging without high magnification to differentiate polyps during real-time colonoscopy: improvement with experience
Gastrointest Endosc
(2008)
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
Magnifying endoscopy with narrow band imaging for diagnosis of colorectal tumors
Gastrointest Endosc
Systematic review of narrow-band imaging for the detection and differentiation of neoplastic and nonneoplastic lesions in the colon (with videos)
Gastrointest Endosc
Narrow-band imaging without optical magnification for histologic analysis of colorectal polyps
Gastroenterology
A novel tableted purgative for colonoscopic preparation: efficacy and safety comparisons with Colyte and Fleet Phospho-Soda
Gastrointest Endosc
The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement: guidelines for reporting observational studies
Lancet
How many endoscopies are performed for colorectal cancer screening? Results from CDC's survey of endoscopic capacity
Gastroenterology
Sporadic and syndromic hyperplastic polyps and serrated adenomas of the colon: classification, molecular genetics, natural history, and clinical management
Gastroenterol Clin North Am
Accuracy of pathologic interpretation of colorectal polyps by general pathologists in community practice
Gastrointest Endosc
Diagnosis of colorectal tumorous lesions by magnifying endoscopy
Gastrointest Endosc
A pooled analysis of advanced colorectal neoplasia diagnoses after colonoscopic polypectomy
Gastroenterology
Adenoma size and number are predictive of adenoma recurrence: implications for surveillance colonoscopy
Gastrointest Endosc
Narrow-band imaging colonoscopy—a pilot feasibility study for the detection of polyps and correlation of surface patterns with polyp histologic diagnosis
Gastrointest Endosc
President's address: the polyp-cancer sequence in the large bowel
Proc R Soc Med
Prevention of colorectal cancer by colonoscopic polypectomy: the National Polyp Study Workgroup
N Engl J Med
Cited by (317)
Colon cancer stage detection in colonoscopy images using YOLOv3 MSF deep learning architecture
2023, Biomedical Signal Processing and ControlImplementation of optical diagnosis with a “resect and discard” strategy in clinical practice: DISCARD3 study
2022, Gastrointestinal EndoscopyThird Eye? The Assistance of Artificial Intelligence (AI) in the Endoscopy of Gastrointestinal Neoplasms
2023, Journal of Clinical Medicine