Barrett's oesophagus: new diagnostic and therapeutic techniques.

BACKGROUND

Barrett's oesophagus is associated with an increased risk of developing adenocarcinoma. Cancer development is preceded by dysplastic changes. Yet, detection of these microscopic changes has remained beyond the reach of routine endoscopy. Endoscopic screening in Barrett's therefore relies mainly on extensive random biopsy sampling.

METHODS

Update on new endoscopic diagnostics techniques for Barrett's oesophagus.

RESULTS

Application of new optical techniques has the potential to enhance our ability to detect dysplasia during endoscopic procedures and take targeted biopsies. Spectral information can be obtained either by point measurements using an optical fibre ('spectral biopsy') or by imaging a broad tissue field. Light-induced fluorescence techniques are based on the observation that tissue when excited by light of shorter wavelength will emit fluorescent light of a longer wavelength. This concept can be used to image tissue in vivo, based on minimal biochemical and structural changes of the (sub)mucosa. Elastic scattering spectroscopy is a spectral biopsy technique that can be exploited even to detect low-grade dysplasia, based on structural information of the mucosa, in which the size and crowding of nuclei in the epithelial layer play a key role. Optical coherence tomography uses reflection of light at optically scattering structures for cross-sectional tissue imaging. Compared to B-scan ultrasonography, optical coherence tomography offers a much higher resolution (10-20 micron), without the need for tissue contact or acoustic coupling. These spectral techniques, although still in their infancy, have already shown the ability to detect early cancer, high-grade dysplasia and in some cases even low-grade dysplasia with a promising degree of sensitivity. As the instruments and the techniques will be further refined, they are likely to become an important part of endoscopic screening. Advances in endoscopic treatment techniques make early malignancies, for which surgical resection is the only accepted therapy, amenable for minimally invasive endoscopic treatment. Endoscopic mucosal resection is a minimally invasive endoscopic technique that can be used in patients with circumscribed mucosal carcinomas. The technique is also useful as a diagnostic procedure by obtaining a full-thickness mucosal specimen for histologic examination. Photodynamic therapy using the prodrug 5-aminolevulinic acid is an ablative therapy that destroys the oesophageal mucosa, leaving the deeper layers of the oesophageal wall intact. Cell damage is achieved by the action of light on the photosensitizing agent protoporphyrin IX in the mucosa, with skin photosensitivity of less than 48 h. Such mucosal ablation, however, can also be accomplished with more common thermal techniques like argon plasma coagulation. In all these ablative procedures, squamous regeneration is obtained by rigorous antacid therapy. In selected patients, these endoscopic ablation methods, although still experimental, might already offer an alternative to oesophagectomy. The need for further improvement, in conjunction with the lack of long-term follow-up data, however, limits the use of these techniques to expert centres.

CONCLUSION

New endoscopic techniques are likely to change the diagnostic and therapeutic procedures for Barrett's oesophagus in the near future.