L. Max Almond

Advances in the clinical application of Raman spectroscopy for cancer diagnostics.

Light interacts with tissue in a number of ways including, elastic and inelastic scattering, reflection and absorption, leading to fluorescence and phosphorescence. These interactions can be used to measure abnormal changes in tissue. Initial optical biopsy systems have potential to be used as an adjunct to current investigative techniques to improve the targeting of blind biopsy. Future prospects with molecular-specific techniques may enable objective optical detection providing a real-time, highly sensitive and specific measurement of the histological state of the tissue. Raman spectroscopy has the potential to identify markers associated with malignant change and could be used as diagnostic tool for the early detection of precancerous and cancerous lesions in vivo. The clinical requirements for an objective, non-invasive, real-time probe for the accurate and repeatable measurement of pathological state of the tissue are overwhelming. This paper discusses some of the recent advances in the field.

Endoscopic Raman spectroscopy enables objective diagnosis of dysplasia in Barrett's esophagus

BACKGROUND Early detection and targeted endoscopic resection of Barretts esophagus-associated high-grade dysplasia (HGD) can prevent progression to invasive esophageal malignancy. Raman spectroscopy, a highly sophisticated analytical technique, has been translated into an endoscopic tool to facilitate rapid, objective diagnosis of dysplasia in the esophagus. OBJECTIVE To evaluate the ability of endoscopic Raman spectroscopy (ERS) to objectively detect esophageal HGD and adenocarcinoma. DESIGN A total of 798 one-second spectra were measured from 673 ex vivo esophageal tissue samples, collected from patients with Barretts esophagus by using a novel endoscopic Raman probe. Spectra were correlated with consensus histopathology. Multivariate analysis was used to evaluate the classification accuracy of ERS ex vivo. SETTING Probe measurements were conducted in the laboratory. Tissue specimens were collected from the operating theatre and endoscopy unit. PATIENTS Tissue from 62 patients was included in the study. INTERVENTIONS Endoscopic biopsy/resection or esophagectomy was performed where indicated clinically. MAIN OUTCOME MEASUREMENT Diagnostic performance of ERS for detection of HGD and esophageal adenocarcinoma. RESULTS ERS demonstrated a sensitivity of 86% and a specificity of 88% for detecting HGD and adenocarcinoma. The ability to grade dysplasia and differentiate intestinal metaplasia from nonintestinal metaplasia columnar-lined esophagus was also demonstrated. Diagnostic classification was based on objective measurement of the biochemical profile of different tissue types. The potential for combination ERS and narrow-band imaging was also demonstrated. LIMITATIONS Measurements were taken from ex vivo tissue. CONCLUSION ERS enables rapid, accurate, objective diagnosis of superficial esophageal disease (metaplasia, dysplasia, intramucosal cancer) in clinically applicable time scales.

Raman spectroscopy: a potential tool for early objective diagnosis of neoplasia in the oesophagus.

There is a profound clinical need for a diagnostic tool that will enable clinicians to identify early neoplastic change in the oesophagus. Raman Spectroscopy (RS) has demonstrated the potential to provide non-invasive, rapid, objective diagnosis of endoscopically invisible precancerous oesophageal dysplasia in vitro. RS analyses biological material to identify highly specific biochemical information that can be used to influence clinical care. Raman spectroscopic mapping could provide automated assessment of tissue biopsies to aid histopathological diagnosis in vitro. Furthermore, the recent development of fibre-optic Raman probes has enabled endoscopic assessment of oesophageal mucosa in vivo. Accurate identification of dysplasia will enable targeted endoscopic resection of early lesions preventing the development of oesophageal cancer. This review summarises the development of Raman systems for use as laboratory based analytical adjuncts and endoscopic diagnostic tools in the distal oesophagus.

Assessment of a custom-built Raman spectroscopic probe for diagnosis of early oesophageal neoplasia

We evaluate the potential of a custom-built fiber-optic Raman probe, suitable for in vivo use, to differentiate between benign, metaplastic (Barretts oesophagus), and neoplastic (dysplastic and malignant) oesophageal tissue ex vivo on short timescales. We measured 337 Raman spectra (λ(ex)=830 nm; P(ex)=60 mW; t=1 s) using a confocal probe from fresh (298) and snap-frozen (39) oesophageal tissue collected during surgery or endoscopy from 28 patients. Spectra were correlated with histopathology and used to construct a multivariate classification model which was tested using leave one tissue site out cross-validation in order to evaluate the diagnostic accuracy of the probe system. The Raman probe system was able to differentiate, when tested with leave one site out cross-validation, between normal squamous oesophagus, Barretts oesophagus and neoplasia with sensitivities of (838% to 6%) and specificities of (89% to 99%). Analysis of a two group model to differentiate Barretts oesophagus and neoplasia demonstrated a sensitivity of 88% and a specificity of 87% for classification of neoplastic disease. This fiber-optic Raman system can provide rapid, objective, and accurate diagnosis of oesophageal pathology ex vivo. The confocal design of this probe enables superficial mucosal abnormalities (metaplasia and dysplasia) to be classified in clinically applicable timescales paving the way for an in vivo trial.

Management controversies in Barrett’s oesophagus

The management of Barrett’s oesophagus and associated neoplasia has evolved considerably in recent years. Modern endoscopic strategies including endoscopic resection and mucosal ablation can eradicate dysplastic Barrett’s and prevent progression to invasive oesophageal cancer. However, several aspects of Barrett’s management remain controversial including the stage in the disease process at which to intervene, and the choice of endoscopic or surgical therapy. A review of articles pertaining to the management of Barrett’s oesophagus with or without associated neoplasia, was conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Medline, Embase and Cochrane databases were searched to identify literature relevant to eight pre-defined areas of clinical controversy. The following search terms were used: Barrett’s oesophagus; dysplasia; intramucosal carcinoma; endotherapy; endoscopic resection; ablation; oesophagectomy. A significant body of evidence exists to support early endoscopic therapy for high-grade dysplasia (HGD). Although not supported by randomised controlled trial evidence, endoscopic therapy is now favoured ahead of oesophagectomy for most patients with HGD. Focal intramucosal (T1a) carcinomas can be managed effectively using endoscopic and surgical therapy, however surgery should be considered the first line therapy where there is submucosal invasion (T1b). Treatment of low grade dysplasia is not supported at present due to widespread over-reporting of the disease. The role of surveillance endoscopy in non-dysplastic Barrett’s remains controversial.

Automated cytological detection of Barrett's neoplasia with infrared spectroscopy.

BackgroundDevelopment of a nonendoscopic test for Barrett’s esophagus would revolutionize population screening and surveillance for patients with Barrett’s esophagus. Swallowed cell collection devices have recently been developed to obtain cytology brushings from the esophagus: automated detection of neoplasia in such samples would enable large-scale screening and surveillance.MethodsFourier transform infrared (FTIR) spectroscopy was used to develop an automated tool for detection of Barrett’s esophagus and Barrett’s neoplasia in esophageal cell samples. Cytology brushings were collected at endoscopy, cytospun onto slides and FTIR images were measured. An automated cell recognition program was developed to identify individual cells on the slide.ResultsCytology review and contemporaneous histology was used to inform a training dataset containing 141 cells from 17 patients. A classification model was constructed by principal component analysis fed linear discriminant analysis, then tested by leave-one-sample-out cross validation. With application of this training model to whole slide samples, a threshold voting system was used to classify samples according to their constituent cells. Across the entire dataset of 115 FTIR maps from 66 patients, whole samples were classified with sensitivity and specificity respectively as follows: normal squamous cells 79.0% and 81.1%, nondysplastic Barrett’s esophagus cells 31.3% and 100%, and neoplastic Barrett’s esophagus cells 83.3% and 62.7%.ConclusionsAnalysis of esophageal cell samples can be performed with FTIR spectroscopy with reasonable sensitivity for Barrett’s neoplasia, but with poor specificity with the current technique.

Strategies for the prevention of oesophageal adenocarcinoma

The incidence of oesophageal adenocarcinoma has increased by 500% over the past 30 years [1]. Improved understanding of the mechanisms of neoplastic progression provides an opportunity to reverse this trend. A thorough review of emerging strategies aiming to prevent the formation of oesophageal malignancy is presented. These include dietary modification, chemoprevention, early endoscopic identification and treatment of premalignant disease, and the potential for a non-endoscopic screening test. Oesophageal adenocarcinoma has become a major public health problem in the West and it is essential that clinicians are fully informed of risk reduction strategies so that they can be actively promoted in the community.

Endoscopic Detection and Eradication of Dysplastic Barrett's Oesophagus

Over the past four decades the incidence of oesophageal cancer has increased more rapidly than that of any other solid tumour in the Western World. This rise reflects the emergence of oesophageal adenocarcinoma as the most common pathological type. Despite this growing incidence, progress towards early detection and treatment has been slow and mortality figures have remained dismal – Cancer Research UK quotes overall one and five year survival rates of just 28% and 8% respectively.(CrUK, 2010) As a result, oesophageal cancer repreasents a real and growing public health problem and urgent action is required to improve detection and facilitate early intervention, ideally at a pre-malignant stage. Most oesophageal adenocarcinoma develops following a well recognised series of cellular changes secondary to a multifactorial aetiology. In the classically described pathway there is initially a metaplastic change in the epithelial lining of the oesophagus (Barrett’s oesophagus) which then progresses to ‘low-grade‘ and then ‘high-grade‘ dysplasia. As many as 30% of patients newly diagnosed with high-grade dysplasia may already have a coexistent invasive cancer, and between 5-60% of patients will develop cancer during surveillance over 1-7 years. To date there is no early diagnostic test which can enable instantaneous accurate diagnosis of dysplasia. Clinicians are advised to take random biopsies from areas of Barrett’s oesophagus in order to identify dysplasia, but even histological assessment of dysplasia is subjective and can be unreliable. As a result, significant dysplastic change (or even intramucosal cancer) may be missed. In addition, as dysplasia (the premalignant lesion) is difficult to identify, screening for early oesophageal cancer / high-grade dysplasia cannot currently be recommended, and as a consequence, oesophageal tumours present late and so have a poor prognosis. The early recognition of high-grade dysplasia is paramount to enabling a successful treatment strategy. Surgery is one option for patients with confimred HGD, however the emergence of multiple endotherapies over the past 20 years have demonstrated the ability to cure focal high-grade dysplasia, thus preventing progression to invasive malignancy. In this chapter we will discuss the accuracy of endoscopic and histological diagnosis of dysplasia and will consider novel endoscopic adjuncts which may improve endoscopic sensitivity. We will then discuss the endoscopic therapeutic options that are available for management of dysplastic Barrett’s oesophagus and will propose a endotherapy algorithm for use in specialist Barrett’s surveillance centres.