Long-term endoscopic surveillance of Barrett's esophagus

Genetic mechanisms of TP53 loss of heterozygosity in Barrett's esophagus: implications for biomarker validation

BACKGROUND AND AIMS

17p (TP53) loss of heterozygosity (LOH) has been reported to be predictive of progression from Barrett's esophagus to esophageal adenocarcinoma, but the mechanism by which TP53 LOH develops is unknown. It could be (a) DNA deletion, (b) LOH without copy number change, or (c) tetraploidy followed by genetic loss. If an alternative biomarker assay, such as fluorescence in situ hybridization (FISH), provided equivalent results, then translation to the clinic might be accelerated, because LOH genotyping is presently limited to research centers.

METHODS

We evaluated mechanisms of TP53 LOH to determine if FISH and TP53 LOH provided equivalent results on the same flow-sorted samples (n = 43) representing established stages of clonal progression (diploid, diploid with TP53 LOH, aneuploid) in 19 esophagectomy specimens.

RESULTS

LOH developed by all three mechanisms: 32% had DNA deletions, 32% had no copy number change, and 37% had FISH patterns consistent with a tetraploid intermediate followed by genetic loss. Thus, FISH and LOH are not equivalent (P < 0.000001).

CONCLUSIONS

LOH develops by multiple chromosome mechanisms in Barrett's esophagus, all of which can be detected by genotyping. FISH cannot detect LOH without copy number change, and dual-probe FISH is required to detect the complex genetic changes associated with a tetraploid intermediate. Alternative biomarker assay development should be guided by appreciation and evaluation of the biological mechanisms generating the biomarker abnormality to detect potential sources of discordance. FISH will require validation in adequately powered longitudinal studies before implementation as a clinical diagnostic for esophageal adenocarcinoma risk prediction.

Endoprevention of esophageal cancer: endoscopic ablation of Barrett's metaplasia and dysplasia

This review describes the use of endoscopic therapy for the treatment of Barrett's disease and the prevention of esophageal carcinoma, predominantly a disease of older white men. While the term endoprevention may be novel, gastroenterologists have been using endoscopic techniques to prevent colon cancer for decades. For the endoprevention of Barrett's carcinoma, the regulatory approval for the use of porfimer sodium photodynamic therapy was an important milestone, as this treatment has been proven to safely ablate Barrett's glandular epithelium, including high-grade dysplasia, and significantly decrease the risk for the development of invasive cancer in several single-center studies, a prospective multicenter randomized controlled study using expert centralized histopathology analysis and long-term single-center results. Newer methods of mucosal ablation, such as the radiofrequency balloon, have been developed for the treatment of patients with Barrett's metaplasia or dysplasia. These newly developed techniques are able to treat large fields of glandular epithelium in a short treatment procedure using safe, effective, durable methods for the complete ablation of Barrett's metaplasia and low-grade dysplasia. These techniques may finally allow the interventional gastrointestinal endoscopist to prevent the development of esophageal carcinoma, just as colonoscopy with polypectomy has prevented colon cancer. However, it will be critically important to document the safety, durability and efficacy of these devices. Ultimately, the impact of successful Barrett's ablation on the incidence of Barrett's carcinoma, and the need for postablation surveillance endoscopy must be determined.

Photodynamic therapy for Barrett's esophagus with high-grade dysplasia

This article describes advances in photodynamic therapy for patients with Barrett's esophagus and high-grade dysplasia-an important, minimally invasive treatment option proven to safely and durably ablate Barrett's dysplasia and prevent carcinoma while preserving the gastroesophageal junction.

Analysis of protein expression patterns in Barrett's esophagus using MALDI mass spectrometry, in search of malignancy biomarkers

In order to detect early changes of malignant degeneration in Barrett's esophagus (BE), and to reduce the cost of surveillance, molecular biomarkers of early malignancy have been sought, with limited success, using genomic and immunohistochemical tools. We postulate that direct analysis of epithelial proteins using mass spectrometry will provide protein profiles capable of identifying patients at high risk of developing malignancy. Our aim is to find transitional protein signals that show a cancer profile within histologically benign BE, which can be used as indicators of early malignant change. Fourteen fresh-frozen, resected esophageal cancer specimens were analyzed using laser capture microdissection and matrix-assisted laser desorption/ionization mass spectrometry. Samples of squamous epithelium, and both benign and malignant Barrett's epithelium, were compared for differences in protein expression. Reliable differentiation of squamous and Barrett's epithelium was demonstrated. A comparison of benign and malignant Barrett's epithelium identified a number of cancer-specific protein peaks that were deletion or expression variations from benign epithelium. In four instances the proteins (7350, 8446, 10850, and 14693) appeared to be early malignant changes in histologically benign BE. Mass spectrometry performed upon fresh-frozen Barrett's epithelium, obtained by laser-capture microdissection, displays reproducible, tissue-specific, protein profiles. Distinct differences are demonstrated between benign and malignant epithelium, some of which appear to be candidate biomarkers of early malignant change. This technique reliably displays cellular protein expression in esophageal epithelium and deserves further study as a tool to identify early malignant degeneration in BE.

Present status of photodynamic therapy for high-grade dysplasia in Barrett's esophagus

GOALS

Review recent developments in Barrett's dysplasia including regulatory approval of porfimer sodium photodynamic therapy.

BACKGROUND

Barrett's esophagus is thought to be the result of long-standing gastroesophageal reflux disease and is known to be the most important risk factor for the development of esophageal adenocarcinoma. The natural history of Barrett's esophagus is not well known, but the annual incidence of invasive adenocarcinoma is estimated to be 0.5% (reported range, 0.2%-2.0%). This represents an increased risk for esophageal cancer of 30 to 60 times higher than normal subjects. As for colorectal cancer, malignant degeneration is Barrett's esophagus is thought to occur through a continuum of histologic stages: metaplasia, dysplasia and neoplasia. Barrett's high-grade dysplasia (formerly referred to as carcinoma in situ) is the histologic stage of disease that immediately precedes the development of invasive carcinoma.

CONCLUSIONS

Previously, Barrett's high-grade dysplasia patients were routinely referred for esophageal resection surgery based upon the assumption of inevitable progression to cancer, the high rate of undiagnosed synchronous cancers, and few treatment alternatives. Important developments in Barrett's high-grade dysplasia include recent publications regarding the natural history of Barrett's high-grade dysplasia and the regulatory approval for endoscopic ablation therapy using porfimer sodium photodynamic therapy (Photofrin PDT).

Clinical experience of patients undergoing photodynamic therapy for Barrett's dysplasia or cancer

INTRODUCTION

Barrett's oesophagus is the most important risk factor in the increase in incidence of oesophageal adenocarcinoma. Photodynamic therapy using porfimer sodium is the only approved endoscopic treatment for use in patients with Barrett's high-grade dysplasia.

AIM

To determine clinical characteristics, endoscopic findings and treatment complications in Barrett's high-grade dysplasia patients undergoing photodynamic therapy.

METHODS

We reviewed our experience using porfimer sodium photodynamic therapy to treat patients with Barrett's oesophagus and high-grade dysplasia or mucosal carcinoma. Data collected included patients characteristics, presentation symptoms, endoscopic findings, subsequent use of surveillance endoscopy and outcome after photodynamic therapy.

RESULTS

Since 1997, 102 patients with Barrett's high-grade dysplasia (69 patients) or mucosal adenocarcinoma (33 patients) have been treated with photodynamic therapy using porfimer sodium as an alternative to oesophagectomy (median series follow-up time = 1.6 years). Almost half (46%) of patients had high-grade dysplasia or carcinoma detected on their first endoscopy and the remainder (54%) were found during surveillance of known Barrett's oesophagus. Symptoms typically associated with oesophageal disease were only found in 29 of 47 (62%) patients in whom dysplasia/carcinoma was detected on the initial endoscopy - chest pain in 13 patients, dysphagia in nine patients and chronic gastro-oesophageal disease in seven patients. Comparison of endoscopic characteristics found the median Barrett's glandular segment length was significantly shorter in adenocarcinoma patients (median 3 cm; range: 1-12) vs. Barrett's high-grade dysplasia patients (median 5 cm; range: 1-16, P < 0.001). Overall treatment results found complete ablation of glandular epithelium with one course of photodynamic therapy in most patients (56%). Stricture requiring dilation occurred in 20 patients (20%) was the most common serious adverse event. Photodynamic therapy failed to ablate dysplasia or carcinoma in four patients and subsequent oesophagectomy was curative in three of these patients.

CONCLUSIONS

Approximately 40% of newly diagnosed patients with Barrett's associated dysplasia or carcinoma had no oesophageal symptoms and had carcinoma associated with short segment (3 cm or less). Photodynamic therapy is a highly effective, safe and minimally invasive first-line treatment for patients with Barrett's dysplasia and mucosal adenocarcinoma.