Magnification chromo-colonoscopy

Should We Resect and Discard Low Risk Diminutive Colon Polyps

Diminutive colorectal polyps <5 mm are very common and almost universally benign. The current strategy of resection with histological confirmation of all colorectal polyps is costly and may increase the risk of colonoscopy. Accurate, optical diagnosis without histology can be achieved with currently available endoscopic technologies. The American Society of Gastrointestinal Endoscopy Preservation and Incorporation of Valuable endoscopic Innovations supports strategies for optical diagnosis of small non neoplastic polyps as long as two criteria are met. For hyperplastic appearing polyps <5 mm in recto-sigmoid colon, the negative predictive value should be at least 90%. For diminutive low grade adenomatous appearing polyps, a resect and discard strategy should be sufficiently accurate such that post-polypectomy surveillance recommendations based on the optical diagnosis, agree with a histologically diagnosis at least 90% of the time. Although the resect and discard as well as diagnose and leave behind approach has major benefits with regard to both safety and cost, it has yet to be used widely in practice. To fully implement such as strategy, there is a need for better-quality training, quality assurance, and patient acceptance. In the article, we will review the current state of the science on optical diagnose of colorectal polyps and its implications for colonoscopy practice.

New paradigms in polypectomy: resect and discard, diagnose and disregard

Polypectomy at colonoscopy has been shown to reduce the subsequent risk of colorectal cancer. With the advent of national screening programs, the number of colonoscopies performed has increased worldwide. In addition, the recent drive for quality improvement combined with advances in colonoscopic technology has resulted in increased numbers of polyps detected, resected, and sent for histopathology leading to spiraling costs associated with the procedure. Being able to diagnose small polyps in vivo (optical diagnosis) would allow for adenomas to be resected and discarded without the need to retrieve them or send them for formal histopathology.

Dual optical modality endoscopic imaging of cancer development in the mouse colon

BACKGROUND AND OBJECTIVE

We utilize a miniature, dual-modality endoscope that combines fluorescence-based surface magnifying chromoendoscopy (SMC) and optical coherence tomography (OCT) to follow the anatomical changes that occur during adenoma development in the mouse colon.

MATERIALS AND METHODS

Twenty-five mice were treated with the carcinogen azoxymethane (AOM) to induce tumor development in the distal colon, or were treated with saline as control, and were imaged over six months. OCT detects adenoma number with high sensitivity and specificity and can measure lesion size. In methylene blue-lavaged colons, SMC detects changes in the colonic crypts. SMC images of control mouse colons exhibit reticulated patterns of crypts of equal size, forming either a dot or honeycomb pattern.

RESULTS

Images of AOM-treated colons show mild crypt irregularities even in grossly normal tissue. Images of small to medium adenoma exhibit larger crypts, more intense signal, and irregular spacing whereas those of large adenoma have heterogeneous, intense signal and loss of crypt structure.

CONCLUSIONS

The combination of OCT and SMC permits the detection of neoplastic events from the earliest stages of crypt irregularities before gross tissue changes are noted, through to measuring the growth of protruding adenoma.

NBI and NBI Combined with Magnifying Colonoscopy

Although magnifying chromoendoscopy had been a reliable diagnostic tool, narrow-band imaging (NBI) has been developed in Japan since 1999 and has now replaced the major role of chromoendoscopy because of its convenience and simplicity. In this paper, we principally describe the efficacy of magnifying chromoendoscopy and magnifying colonoscopy with NBI for detection, histological prediction, estimation of the depth of early colorectal cancer, and future prospects. Although some meta-analyses have concluded that NBI is not superior to white light imaging for detection of adenomatous polyps in screening colonoscopy, NBI with magnification colonoscopy is useful for histological prediction, or for estimating the depth of invasion. To standardize these diagnostic strategies, we will focus on the NBI International Colorectal Endoscopic (NICE) classification proposed for use by endoscopists with or without a magnifying endoscope. However, more prospective research is needed to prove that this classification can be applied with satisfactory availability, feasibility, and reliability. In the future, NBI might contribute to the evaluation of real-time histological prediction during colonoscopy, which has substantial benefits for both reducing the risk of polypectomy and saving the cost of histological evaluation by resecting and discarding diminutive adenomatous polyps (resect and discard strategy).

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

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.