Colorectal cancer (CRC) represents the third most common cancer worldwide with incidence varying depending on geographical location.1 Colonoscopy serves as the major screening and diagnostic tool for detecting CRC; however, there are other modalities such as virtual colonoscopy, flexible sigmoidoscopy, and fecal occult blood testing (with or without immunohistochemical testing). As with any screening test, there is always the possibility of missing either a precancerous or cancerous lesion. Currently, the “miss rate” for colonic adenomas during colonoscopy has been reported at between 15% and 32%.1 Consequently, this miss rate has been shown to correspond to 1 out of 13 of all CRCs being diagnosed after a “negative” colonoscopy. 

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There is a great deal of interest in identifying ways to improve adenoma and polyp detection, including the enhancement of images visualized during colonoscopy. One potential modality is the use of narrow band imaging (NBI) during colonoscopy, which uses a special filter to reportedly improve visualization of blood vessels and mucosal patterns associated with polyps or adenomas. However, several meta-analyses have failed to show a difference between NBI and the traditional high-definition white light (HD-WL) colonoscopy with respect to colonic polyp detection.2,3 In an attempt to improve the NBI system, a newer, second-generation NBI (190-NBI) has been developed, which includes at least a two-fold brighter image compared with the first version. Recently, Leung et al conducted a study to compare the second generation 190-NBI to HD-WL with respect to adenoma and polyp detection and miss rates.1 

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In this prospective trial, a total of 360 patients were randomly assigned to colonoscopy with either 190-NBI or HD-WL. Patients underwent colonoscopy for screening, surveillance, or were symptomatic. Adenoma and polyp detection rates were statistically significantly higher in the 190-NBI group (48.3% and 61.1%, respectively) compared with the HD-WL (34.4% and 48.3%). A higher mean number of polyps were detected in the 190-NBI group compared with the HD-WL group, but this difference was not statistically significant. In addition, there was no difference in the detection rate of advanced colorectal neoplasms between the two groups.  Although the adenoma and polyp detection rates were higher in the 190-WBI group, the miss rate was not different between the groups (21.8% 190-NBI, 21.2% HD-WL).  It is worth noting that this study was conducted at a single center in Hong Kong and enrolled only Chinese patients. Also, there was no comparison with the first generation of NBI, which may have been interesting to include for additional comparisons. 

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Although colonoscopies performed with 190-NBI appeared to show some promise in this most recent study, it still did not show any difference in miss rates.  Future studies and technology will undoubtedly focus on reducing the miss rate.

References

  1. Leung WK, Lo OS, Liu KS, et al.  Detection of colorectal adenoma by narrow band imaging (HQ190) vs. high-definition white light colonoscopy: a randomized controlled trial. Am J Gastroenterol. 2014;109(6):855-863.
  2. Dinesen L, Chua TJ, Kaffes AJ. Meta-analysis of narrow-band imaging versus conventional colonoscopy for adenoma detection. Gastrointest Endosc. 2012;75(3):604-611.
  3. Pasha SF, Leighton JA, Das A, et al. Comparison of the yield and miss rate of narrow band imaging and white light endoscopy in patients undergoing screening or surveillance colonoscopy: a meta-analysis. Am J Gastroenterol. 2012;107(3):363-370

Topics:

Colonoscopy Colorectal Cancer Gastrointestinal Cancer In The Clinic