**4.7 Labelling of biomarkers**

154 Gastrointestinal Endoscopy

adenocarcinoma. Staining and lesion defining agents utilised include methylene blue, indigo carmine, and acetic acid. Results from studies utilising this technique have been mixed citing problems such as an inability to uniformly coat the oesophageal mucosa with the stain, and excessive time necessary for stain spraying as particular concerns.(Shaheen and Richter, 2009; Lim et al., 2006; Ragunath et al., 2003) None of these techniques has been shown to consistently out-perform high resolution endoscopy in the detection of early neoplastic lesions.(Curvers et al., 2008c) Chromoendoscopy is often both labour-intensive and operator-dependent and therefore although it may have a role when used in specialist centres by expert users, it is unlikely to develop a wider role in routine clinical practice.

NBI filters white light into blue and green wavelengths (at the push of a button) giving more accurate images of the mucosal and vascular patterns in the oesophageal lining. This increased superficial imaging of the oesophagus (without the need for staining) can be used to identify dysplastic lesions within Barrett's segments.(Kara et al., 2006a) In the hands of experienced users the technique has shown promise however, results have been mixed.(Sharma et al., 2006a; Curvers et al., 2008a) A recent trial from Holland shows no diagnostic benefit from either NBI or chromoendoscopy.(Curvers et al., 2008a) However, data on the accuracy of NBI is still inconclusive and results of ongoing mulitcentre

Following excitation with short wavelengths of light many endogenous tissues emit fluorescence radiation which can be measured using fluorescence spectroscopy. Metaplastic and dysplastic Barrett's oesohagus have been shown to emit slightly different fluorescence spectra enabling the technique to be used as a mechanism to discriminate between the two pathologies. AFI appears to improve the detection of early Barrett's neoplasia when used in combination with high resolution endoscopy, although the false positive rate is relatively high.(Curvers et al., 2008b; Kara et al., 2005b; Kara et al., 2006b) Further studies are clearly

OCT is analogous to ultrasound but can produce higher quality images as it relies on scattering of near infrared light as opposed to reflection of sound waves. OCT can obtain cellular images of sub-epithelial tissue through differences in their light scattering properties

In a study of 55 patients with Barrett's oesophagus, OCT was shown to delineate between HGD and oesophageal adenocarcinoma with a sensitivity of 83% and a specificity of 75%.(Evans et al., 2006) Similarly, a study of 33 patients demonstrated a diagnostic accuracy of 78% for the identification of dysplastic Barrett's oesophagus but with considerable user discrepency (56% to 98%). (Isenberg et al., 2005) Further clinical evaluation is required to fully assess the performance of OCT and assess the feasibility of introducing this promising

CM magnifies the mucosa by more than 1000 fold producing images with 1-2 µm spatial resolution and allowing real time visualisation of cellular structures. Kiesslich et al studied

**4.3 Narrow band imaging (NBI)** 

randomised controlled trials are awaited.

**4.5 Optical coherence tomography (OTC)** 

diagnostic tool into routine clinical practice.

**4.6 Confocal microscopy (CM)** 

and avoids the need for exogenous contrast material.

indicated to truely assess the potential long-term role for AFI.

**4.4 Autofluorescence imaging (AFI)** 

Molcular biomarkers associated with neoplastic cells can be labelled using a specifically targetted probe molecule which has been tagged with a visual agent such as a fluoresecent dye. (Pierce et al., 2008) (Thekkek et al., 2011) The probe molecule selectively binds to the biomarker so that areas of neoplasia can be visualised with a high signal to noise ratio.

Lu et al identified a cell surface peptide specific to adenocarcinoma which they labelled using a fluorescein-tagged antibody delivered topically. The oesophagus was then washed to remove any unbound antibody and a fluorescence endoscope was used to visualise neoplastic disease. (Lu and Wang, 2008)

Other similar studies have used a range of potential biomarkers with similar effect. This is clearly a very promising technique for the detection of early neoplasia but further on-going work is necessary to identify novel molecular targets in order to improve sensitvity and specificity before widespread implementation of the technique can be contemplated.

#### **4.8 Raman spectroscopy**

Raman spectroscopy is an optical diagnostic technique which has shown considerable potential for early diagnosis of a variety of malignant disease states including oesophageal neoplasia. Raman spectroscopy measures the molecular-specific, inelastic scattering of laser light within tissue in order to generate a unique molecular 'fingerprint'. Normal, dysplastic and cancerous tissues have differing biochemical cellular components leading to characteristic spectral differences which can be analysed. Laboratory based Raman spectrometers are capable of discriminating between eight pathological groups in the distal oesophagus (including Barrett's metaplasia, HGD and adenocarcinoma) with sensitivities between 73% and 100%. (Kendall et al., 2003) Several groups are currently investigating the potential for endoscopic Raman spectroscopy using a fibre-optic Raman probe. Fibreoptic Raman sectroscopy has already demonstrated encouraging results following in vivo trials in the stomach, bladder and cervix. Although some way off clinical implementation in the oesohagus, in vivo and ex vivo results are promissing and this technique may become widely available in the short to medium term to enable instant endoscopic diagnosis of dyslasia (without the need for biopsy) and to facilitate immediate, targetted endotherapy.

Endoscopic Detection and Eradication of Dysplastic Barrett's Oesophagus 157

The current BSG guidelines from 2005 do not recognise the diagnostic role of ER. However, new guidelines are currently being formulated by an international consensus group the 'Barrett's Dysplasia and Cancer Taskforce' (BAD CAT). These will stress the need for extremely accurate assessment of the presence and depth of invasive cancer and will recommend confirmation using ER, as well as (when indicated) further staging using endoscopic ultrasound (EUS) (which is known to be poor at differentiating between T1a and

Recent studies have demonstrated the importance of accurate staging of early (T1) tumours. T1a lesions (confined to the mucosa) have a very low incidence of lymphatic invasion (<5%) whereas, invasion into the submucosa (T1b) is associated with lymphatic spread in 20-45% of cases. New evidence has suggested that the distinction between T1sm1 and T1sm2 (i.e. between the upper 1/3 and lower 2/3 of the submucosa) may be particularly significant as the risk of lymphatic spread appears to significantly increase in T1sm2 tumours. This distinction is vital as surgical oesophagectomy and lymphadenectomy provide the only chance of cure for patients with lymphatic spread, whereas endoscopic therapy is

As histopathological diagnosis and grading of dysplasia is difficult and subjective, any suggestion of dysplasia should be reviewed by expert pathologists at an MDT prior to initiation of a management plan. In cases where exact histopathological diagnosis proves difficult clinicians should have a low threshold for 'diagnostic' endoscopic resection to aid histological classification. This may be of particular benefit in distinguishing between HGD

Once an accurate diagnosis has been made and corroborated by consensus opinion in an MDT, a management plan can be formulated. All patients should be commenced on high dose PPI therapy. Subsequent management is currently subject to significant debate but is largely dependent on the degree of dysplasia, patient comorbidity and patient preference. Recent developments have led to potentially curative endoscopic treatments for HGD and early mucosal cancer. Many of these techniques are relatively novel and are not supported by highest level evidence (RCTs). BSG and American College of Gastroenterology (ACG) guidelines from 2005 and 2008 respectively are now somewhat out-of-date when considering the management of advanced dysplasia / early cancer. However, the management of LGD has not altered in recent years as a simple 'number needed to treat' analysis confirms that the limited risks posed by LDG (in isolation), do not warrant the cost and morbidity imposed

The management of HGD and intramucosal cancer (T1a) is currently hotly debated and new guidelines are awaited (BAD CAT consensus). It is clear that management policies must be individualised according to the nature and severity of disease and the age and comorbidity of the patient being treated, and all management decisions must be discussed at a specialist

There are two main forms of endoscopic therapy available to treat HGD and intramucosal tumours – endoscopic resection and endoscopic ablation. These techniques aim to destroy the lining of the oesophagus and promote regenerative re-growth of normal squamous mucosa. In order for this to occur, (as opposed to columnar re-growth) some of the superficial squamous lined ducts must survive the process. Techniques for mucosal ablation include photodynamic

therapy, thermal ablation, radiofrequency ablation and argon plasma coagulation.

and early invasive (T1) carcinoma, and in accurately T-staging these early cancers.

T1b tumours but is sensitive for lymph node metastases), and possibly PET-CT.

potentially curative in those without lymphatic invasion.

**7. Endoscopic therapies for HGD and IMC** 

by endoscopic therapies.

cancer MDT.
