High Definition Endoscopy With i-Scan for Small Colonic Polyp Evaluation: The HiScope Study
Condition: Colonic Polyps
MeSH terms: Polyps; Colonic Polyps
Study type: Observational

Summary: 
      Current standard practice is to remove all colonic polyps found during colonoscopy as it has
      not been possible to distinguish between polyps with some malignant potential (adenomatous)
      and those with negligable malignant potential (non-adenomatous).

      Recent advances in endoscope imaging and technology have allowed endoscopists to distinguish
      between these two types of polyps by examining minute surface details.

      i-Scan is a new digital enhancement method that aims to enhance surface details and may
      enable similar accurate distinction between adenomatous and non-adenomatous polyps.

      Hypothesis:

      High definition white light endoscopy plus i-Scan improves diagnostic accuracy of in-vivo
      assessment of colonic polyps <10mm in size over high definition white light endoscopy alone.
    

Detailed description: 
      Traditionally all polyps detected at colonoscopy, except obvious cancers, have been removed.
      It is felt that small (<10mm diameter) hyperplastic polyps cannot be reliably distinguished
      from adenomatous polyps by endoscopists [1]. Therefore a large number of hyperplastic polyps
      are removed unnecessarily. This results in increased risk to patients through exposing them
      to unnecessary polypectomy, and increased cost to the health service through the cost of
      processing greater numbers of histopathology specimens. The cost per specimen is around £58.

      This challenge of distinguishing small hyperplastic polyps from small adenomatous polyps has
      been met over the past decade through the use of novel chromoendoscopy and computed 'virtual
      chromoendoscopy' techniques.

      Chromoendoscopy involves using staining or contrast dyes to highlight the minute surface
      patterns in the mucosa of the gastrointestinal tract. The dyes are applied to the colonic
      mucosa via the working channels of the endoscope. Vital stains such as cresyl violet and
      methylene blue, which are taken up into epithelial cells, have been used by Japanese
      endoscopists for many years. Work by Kudo et al showed that by using these stains in
      combination with magnification endoscopy the minute 'pit patterns' of colonic mucosal lesions
      could be precisely examined and classified. The pits described are the surface opening of the
      mucosal crypts. Kudo showed that the surface pit pattern could predict the histology of a
      lesion with high accuracy [2-4], enabling distinction between adenomatous and hyperplastic
      polyps. Concerns regarding potential harmful effects of vital stains increased the popularity
      of an alternative chromoendoscopy dye, indigocarmine [5]. Indigocarmine is not taken up by
      cells but lies on the colonic wall. Studies from East Asia, the USA and Europe published in
      the early part of the last decade showed that by combining indigocarmine and magnification
      endoscopy, neoplastic colonic polyps (adenomas) could be distinguished from non-neoplastic
      hyperplastic polyps with accuracy rates of 68-96% [6-10]. By the same method, surface
      patterns could also identify small early colorectal cancers[11] . Subsequent studies
      demonstrated that indigocarmine could adequately distinguish between adenomatous and
      hyperplastic polyps without the need for optical magnification [12-15].

      During the past few years new methods of closely examining lesions within the colon have been
      developed. Digital imaging techniques or 'virtual chromoendoscopy' systems have been
      developed by endoscope manufacturers as a 'push-button' alternative to chromoendoscopy dyes,
      being potentially simpler and quicker to use. The first of these novel technologies available
      was the narrow band imaging (NBI) system produced by Olympus. A filter within the endoscope
      selects out narrow bandwidths of blue and green light, and thus reduces red light. These
      wavelengths penetrate only the superficial layers of the mucosa, highlighting surface
      patterns and microvasculature. Adenomatous polyps have more numerous and prominent
      microvessels in comparison to hyperplastic poylps. This system has been shown to be effective
      in differentiating small hyperplastic and adenomatous polyps with accuracies of 91 - 94%
      [16-23].

      The Fujinon Intelligent Colour Enhancement (FICE) system developed by Fujinon uses
      post-processor electronic colour filter technology to allow a range of filter images with
      different wavelengths of light to be viewed. Similar results to NBI have been achieved in the
      characterisation of small polyps [13, 24, 25].

      More recently a further virtual chromoendoscopy system, i-Scan has been developed by Pentax.
      i-Scan identifies areas of contrast between adjacent pixels (ie light bordering dark) and
      enhances this contrast. Additionally in a similar method to FICE, post-processor manipulation
      of the red, green and blue components of the spectrum is used to enhance vessels and surface
      structures.

      A single study from Germany has suggested that i-Scan improves the detection of lesions
      during flexible sigmoidoscopy and can accurately predict histology. There is a need for
      further data on the clinical efficacy of i-Scan in the assessment of colonic polyps,
      particularly in a UK population and in a bowel cancer screening population, neither of which
      have been studied to date.

      Through the use of these new technologies it may be possible to accurately predict the
      histology of small polyps in real time. Once an in-vivo diagnosis has been made with high
      confidence it may be possible for small hyperplastic polyps to be discarded, rather than sent
      for histological analysis, or to be left in situ [22]. This has potential benefits in
      reducing the frequency and consequent risk of polypectomy for patients and could also reduce
      pathology costs. UK and US guidelines for repeat surveillance colonoscopy after adenomas are
      detected at baseline examination are based on the number and size and histology of adenomas
      [26, 27]. At present these 'rescope intervals' are determined once the histology report of
      any resected polyps is received. With accurate in-vivo diagnosis these intervals may be set
      immediately after the baseline colonoscopy has been completed.

      Whilst the development of these endoscopic advanced imaging technologies is to be welcomed,
      it is important for studies to determine what can be achieved through their use, over and
      above standard white-light colonoscopy. The American Society for Gastrointestinal Endoscopy
      has identified the utility of technologies used in the real-time assessment of diminutive
      (<5mm) colonic polyps as a key area for study, and has published guidelines on the minimum
      standards which new endoscopic technologies should meet before their use becomes widely
      adopted [28].

      We aim to evaluate HDWL and HDWL + i-Scan for the real time assessment and prediction of
      histology of small colonic polyps in a BCSP population.
    

Intervention name(s): High definition white light endoscopy
Intervention type(s): Procedure
Observational model: Cohort
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        UK Bowel Cancer Screening patients attending for colonoscopy
      
Keywords: Colonic polyps