Endoscopic ultraviolet-induced autofluorescence spectroscopy of the esophagus: tissue characterization and potential for early cancer diagnosis

The informativeness of the Johns-matrix image of laser autofluorescence in blood plasma films for early diagnosis of endometriosis associated with infertility

We used Jones-matrix images of protein networks of blood plasma films obtained from laser autofluorescence and determined the sensitivity, specificity, accuracy, and prognostication of positive and negative results. Our study aimed (1) to develop and substantiate new approaches for the diagnosis of endometriosis by improving the methods of Jones-matrix mapping of laser-induced auto-fluorescence and (2) to develop statistical approaches for analyzing the distribution of values of the true component of Jones-matrix images of blood plasma. Biological preparations were performed for two groups: 35 samples from control group 1 (women with infertility of unknown origin) and 85 samples from group 2 with endometriosis (women with infertility and endometriosis). The strength of the Jones-matrix method of autofluorescence mapping of plasma proteins taken from both groups was maximal for the decisions determined based on the calculation of the statistical moment of the 4^th order, for statistical moment Z4, characterizing the sharpness of the peak distribution of the polycrystalline component of the plasma film. Comparison with the similar informative data of the Jones-matrix laser autofluorescence method of histological sections of the endometrial biopsy under conditions of blind endometriosis diagnosis revealed this method of analysis highly informative. Therefore, this technique can be used in screening studies to form a risk group.

Optical Signatures Derived From Deep UV to NIR Excitation Discriminates Healthy Samples From Low and High Grades Glioma

Among all the tumors of the central nervous system (CNS), glioma are the most deadly and the most malignant. Surgical resection is the standard therapeutic method to treat this type of brain cancer. But the diffusive character of these tumors create many problems for surgeons during the operation. In fact, these tumors migrate outside the tumor solid zone and invade the surrounding healthy tissues. These infiltrative tissues have the same visual appearance as healthy tissues, making it very difficult for surgeons to distinguish the healthy ones from the diffused ones. The surgeon, therefore, cannot properly remove the tumor margins increasing the recurrence risk of the tumor. To resolve this problem, our team has developed a multimodal two-photon fibered endomicroscope, compatible with the surgeon trocar, to better delimitate tumor boundaries by relying on the endogenous fluorescence of brain tissues. In this context, and in order to characterize the optical signature of glioma tumors, this study offers multimodal and multi-scaled optical measurements from healthy tissues to high grade glioma. We can interrogate tissue from deep ultra-violet to near infrared excitation by working with spectroscopy, fluorescence lifetime imaging, two-photon fluorescene imaging and Second Harmonic Generation (SHG) imaging. Optically derived ratios such as the Tryptophan/Collagen ratio, the optical redox ratio and the long lifetime intensity fraction, discriminated diseased tissue from its normal counterparts when fitted by Gaussian ellipsoids and choosing a threshold for each. Additionally two-photon fluorescence and SHG images were shown to display similar histological features as Hematoxylin-Eosin stained images.

Accuracy of autofluorescence in diagnosing oral squamous cell carcinoma and oral potentially malignant disorders: a comparative study with aero-digestive lesions

Presently, various studies had investigated the accuracy of autofluorescence in diagnosing oral squamous cell carcinoma (OSCC) and oral potentially malignant disorders (OPMD) with diverse conclusions. This study aimed to assess its accuracy for OSCC and OPMD and to investigate its applicability in general dental practice. After a comprehensive literature search, a meta-analysis was conducted to calculate the pooled diagnostic indexes of autofluorescence for premalignant lesions (PML) and malignant lesions (ML) of the oral cavity, lung, esophagus, stomach and colorectum and to compute indexes regarding the detection of OSCC aided by algorithms. Besides, a u test was performed. Twenty-four studies detecting OSCC and OPMD in 2761 lesions were included. This demonstrated that the overall accuracy of autofluorescence for OSCC and OPMD was superior to PML and ML of the lung, esophagus and stomach, slightly inferior to the colorectum. Additionally, the sensitivity and specificity for OSCC and OPMD were 0.89 and 0.8, respectively. Furthermore, the specificity could be remarkably improved by additional algorithms. With relatively high accuracy, autofluorescence could be potentially applied as an adjunct for early diagnosis of OSCC and OPMD. Moreover, approaches such as algorithms could enhance its specificity to ensure its efficacy in primary care.

Emerging enhanced imaging technologies of the esophagus: spectroscopy, confocal laser endomicroscopy, and optical coherence tomography

BACKGROUND

Despite advances in diagnoses and therapy, esophageal adenocarcinoma remains a highly lethal neoplasm. Hence, a great interest has been placed in detecting early lesions and in the detection of Barrett esophagus (BE). Advanced imaging technologies of the esophagus have then been developed with the aim of improving biopsy sensitivity and detection of preplastic and neoplastic cells. The purpose of this article was to review emerging imaging technologies for esophageal pathology, spectroscopy, confocal laser endomicroscopy (CLE), and optical coherence tomography (OCT).

METHODS

We conducted a PubMed search using the search string "esophagus or esophageal or oesophageal or oesophagus" and "Barrett or esophageal neoplasm" and "spectroscopy or optical spectroscopy" and "confocal laser endomicroscopy" and "confocal microscopy" and "optical coherence tomography." The first and senior author separately reviewed all articles. Our search identified: 19 in vivo studies with spectroscopy that accounted for 1021 patients and 4 ex vivo studies; 14 clinical CLE in vivo studies that accounted for 941 patients and 1 ex vivo study with 13 patients; and 17 clinical OCT in vivo studies that accounted for 773 patients and 2 ex vivo studies.

RESULTS

Human studies using spectroscopy had a very high sensitivity and specificity for the detection of BE. CLE showed a high interobserver agreement in diagnosing esophageal pathology and an accuracy of predicting neoplasia. We also found several clinical studies that reported excellent diagnostic sensitivity and specificity for the detection of BE using OCT.

CONCLUSIONS

Advanced imaging technology for the detection of esophageal lesions is a promising field that aims to improve the detection of early esophageal lesions. Although advancing imaging techniques improve diagnostic sensitivities and specificities, their integration into diagnostic protocols has yet to be perfected.

Fluorescence imaging for the detection of early neoplasia in Barrett's esophagus: old looks or new vision?

Early neoplasia arising from Barrett's esophagus is often small, focally distributed and endoscopically poorly visible, and random four-quandrant biopsies may easily miss early lesions. Advanced imaging techniques, such as (auto)fluorescence-based modalities, aim to increase the detection rate of early lesions or the yield of random biopsies. Fluorescence-based light-tissue interaction has been designed successfully in point-probe differentiating spectroscopy systems or integrated into wide-field endoscopic systems such as autofluorescence imaging (AFI). In this review, we discuss the most recent advances in fluorescence spectroscopy and imaging for detecting early Barrett's neoplasia. A spectroscopy probe, integrated into regular biopsy forceps, was shown to offer decent discriminatory capabilities, while ensuring spot-on correlation between the measured area and the corresponding histology. With this tool, surveillance endoscopy with random biopsies may become more efficient and sensitive. AFI was shown to increase the targeted detection of early neoplasia. However, random biopsies could compensate for this effect. The clinical impact of AFI on the diagnosis and the treatment of early neoplasia is limited, and yet AFI may offer a novel approach in biomarker-based risk-stratification models. Moreover, in combination with new, readily available contrast agents such as fluorescent lectins, fluorescence imaging may receive renewed interest.

Near-infrared (NIR) laparoscopy for intraoperative lymphatic road-mapping and sentinel node identification during definitive surgical resection of early-stage colorectal neoplasia

BACKGROUND

Appropriate lymphatic assessment is a cornerstone of definitive surgical resection for colorectal cancer. Near-infrared (NIR) laparoscopy may allow real-time intraoperative identification of territorial lymphatic drainage and sentinel nodes in patients with early-stage disease prior to radical basin resection.

METHODS

With IRB approval and individual consent, consecutive patients with radiologically localized neoplasia underwent peritumoral submucosal injection of indocyanine green (ICG, a fluorophore capable of injection site tattooing and efferent lymphatic migration) prior to standard laparoscopic oncological resection. Intraoperatively, a prototype NIR laparoscope provided both white light and, by switch activation, NIR irradiation with or without discrete spectral back-filtration. Fluorescence identification of sentinel nodes prior to formal specimen dissection allowed their identification for separate histopathological analysis by in situ clipping when found within the specimen or selective lymphadenectomy by "berry-picking" when such nodes lay outside of the standard resection field. Concordance with nonsentinel nodes was then analysed.

RESULTS

Eighteen patients (mean age = 66.4 years [range = 47.9-80.1], mean BMI = 29.1 [range = 20.0-39.9]) were studied. Fourteen had biopsy-proven carcinoma and four had endoscopically unresectable dysplasia. Mesocolic sentinel nodes (mean = 4.1/patient) were rendered obvious by fluorescence either solely within the standard resection field (n = 14) or both within and without the planned field (n = 4) within minutes of dye injection in every case. Laparoscopic ultrasound (n = 5) as well as histopathological analysis demonstrated oncologic correlation of mesocolic sentinel with corresponding territory nonsentinel nodes, correctly confirming the presence of mesocolic disease in 3 patients and the absence of such lymphatic spread in the remaining 15 patients.

CONCLUSIONS

In this study, NIR laparoscopy with ICG mapping allowed ready and rapid confirmation of mesocolic lymphatic drainage patterns and sentinel node identification. With further validation, this technology and technique promises precise, tailored resection surgery by indicating basin pattern and status in advance of radical lymphadenectomy.

Autofluorescence and narrow band imaging in Barrett's esophagus

This review discusses the application of 2 novel imaging techniques in Barrett's esophagus: autofluorescence imaging and narrow band imaging (NBI). Autofluorescence as well as NBI may help to direct endoscopic therapy for early neoplasia in Barrett's esophagus; their value in daily practice, however, seems to be limited and needs further evaluation.

Endoscopic imaging for the detection of esophageal dysplasia and carcinoma

Numerous endoscopic imaging modalities have been developed and introduced into clinical practice to enhance diagnostic capabilities. In the past, detection of dysplasia and carcinoma of the esophagus has been dependent on biopsies taken during standard white-light endoscopy. Recent important developments in biophonotics have improved visualization of these subtle lesions sufficiently for cellular details to be seen in vivo during endoscopy. These improvements allow diagnosis to be made in gastrointestinal endoscopy units, thereby avoiding the cost, risk, and time delay involved in tissue biopsy and resection. Chromoendoscopy, narrow-band imaging, high-yield white-light endoscopy, Fujinon intelligent color enhancement, and point enhancement such as confocal laser endomicroscopy are examples of enhanced imaging technologies that are being used in daily practice. This article reviews endoscopic-based imaging techniques for the detection of esophageal dysplasia and carcinoma from the perspective of routine clinical practice.

New technologies for imaging of Barrett's esophagus

There have been many developments in endoscopy-based imaging for the detection of Barrett's syndrome, dysplasia, and neoplasia in patients with Barrett's esophagus. This article reviews the studies on and compares the efficacy of several important endoscopic imaging modalities. Some of these technologies have already achieved regulatory approval, commercial availability, and establishment of clinical utility and practical application. The future of imaging for Barrett's syndrome likely rests with the development of molecular targeting with dysplasiatargeted probes that have been conjugated to dyes or nanoparticles.

Fluorescence and Raman spectroscopy

Reflectance spectroscopy is an emerging technology which provides rapid and safe evaluation of tissue for dysplasia and ischemia. The probe-based devices can be passed through most endoscopes. Current applications include detection of dysplasia in Barrett's esophagus, colitis, and colon polyps.

Novel imaging modalities in the detection of oesophageal neoplasia

The prognosis of oesophageal neoplasia is dependent on the stage of the disease at the time of detection. Early lesions have an excellent prognosis in contrast to more advanced stages that usually have a dismal prognosis. Therefore, the early detection of these lesions is of the utmost importance. In recent years, several new techniques have been introduced to improve the endoscopic detection of early lesions. The most important improvement, in general, has been the introduction of high-resolution/high-definition endoscopy into daily clinical practice. The value of superimposing techniques such as chromoendoscopy, narrow band imaging and computed virtual chromoendoscopy onto high-resolution/high-definition endoscopy will have to be proven in randomised cross-over trials comparing these techniques with standard techniques. Important future adjuncts to white-light endoscopy serving as 'red-flag' techniques for the detection of early neoplasia may be broad field functional imaging techniques such as video autofluorescence endoscopy. In addition, real-time histopathology during endoscopy has become possible with endocytoscopy and confocal endomicroscopy. The clinical value of these techniques needs to be ascertained in the coming years.

Columnar lined (Barrett's) esophagus: future perspectives

Columnar lined esophagus (CLE) or Barrett's esophagus is the precursor for esophageal adenocarcinoma. Future advances in understanding and management of this condition as well as improving the quality of care of CLE patients depends on answering essential questions. It is important to standardize the criteria for CLE definition. The rapid increase in incidence of CLE and adenocarcinoma raises serious concerns that the current management of gastroesophageal reflux disease (GERD) needs reassessment. The risk factors that determine who will and will not develop CLE are as yet undetermined. There is a need to develop a clinical risk stratification tool, which will help in determining who should be screened. The impact of elimination of GERD on the natural history of CLE is one important area for future research. The benefit of surveillance strategies remains unproven and the ideal endoscopic frequency, protocols and markers of cancer risk are unknown. Dysplasia may not provide the gold standard marker of cancer risk because of some inherited problems. A better technique than the current endoscopic pinch biopsy protocol is needed. To overcome the limitations of histological markers, many other markers of cancer risk needs to be developed and validated. The key question as to whether cancer risk is actually reduced by the new ablation modalities remains unanswered. The natural history of dysplasia and its management needs to be clarified. Although many questions have to be answered, it seems, however, that at least some answers exist, and these and proposals for answering some of these questions are underlined throughout this review.

Detection and treatment of dysplasia in Barrett's esophagus: a pivotal challenge in translating biophotonics from bench to bedside

Barrett's esophagus (BE) is a condition that poses high risk of developing dysplasia leading to cancer. Detection of dysplasia is a critical element in determining therapy but is extremely challenging, so that standard white-light endoscopy is used only as a means to guide biopsy. Many novel optical techniques have been aimed at this problem, including various forms of improved wide-field white-light (chromoendscopy/magnification and narrow-band) and fluorescence imaging, and "optical biopsy" techniques (diffuse reflectance, elastic light scattering, fluorescence and Raman spectroscopies, confocal microendoscopy, and optical coherence tomography). While promising, either as stand-alone modalities or in combination, to date none has solved this pivotal challenge to the point of clinical adoption. Likewise, minimally invasive treatment of BE patients with dysplasia remains suboptimal, despite recent approval of photodynamic therapy for this indication. This work presents a critique and summary of each of these biophotonic technologies, and discusses the fundamental advantages and limitations of each. The future directions for this field are considered, particularly from the perspective of relying on intrinsic (endogenous) optical signatures compared with the use of exogenous contrast agents.

Endoscopic video-autofluorescence imaging followed by narrow band imaging for detecting early neoplasia in Barrett's esophagus

BACKGROUND

Video-autofluorescence imaging (AFI) and narrow band imaging (NBI) are new endoscopic techniques that may improve the detection of high-grade intraepithelial neoplasia (HGIN) in Barrett's esophagus (BE). AFI improves the detection of lesions but may give false-positive findings. NBI allows for detailed inspection of the mucosal and (micro)vascular patterns, which are related to HGIN.

OBJECTIVE

A proof-of-principle study to combine AFI and NBI to improve the detection of HGIN and to reduce false-positive findings.

DESIGN

Cross-sectional study of consecutive eligible patients.

SETTING

Single-center.

PATIENTS

Twenty patients with BE with suspected or endoscopically treated HGIN were investigated with 2 prototype imaging systems: AFI (inspection with high-resolution videoendoscopy and autofluorescence imaging for detection of lesions) and NBI (for detailed inspection of mucosal and vascular patterns of identified lesions). Lesions were sampled for histopathologic evaluation.

MAIN OUTCOME MEASUREMENTS

The positive predictive value of AFI alone and of AFI-NBI for detecting HGIN and the reduction of false-positive findings because of the use of NBI.

RESULTS

All of the 28 lesions with HGIN were identified with AFI. Seventeen were identified with white light (61%). Forty-seven suspicious lesions were detected with AFI: 28 contained HGIN (60%) and 19 were false positive (40%). With NBI, 25 of the true-positive lesions had definitely suspicious patterns, and 3 had dubiously suspicious patterns. Of the 19 false positives, 14 were not suspicious on NBI. The false-positive rate, therefore, was reduced from 40% to 10%. Low-grade dysplasia was found in 4 of the remaining 5 false positives. All of the 14 patients with HGIN were identified by AFI-NBI (sensitivity 100%).

LIMITATIONS

Uncontrolled study in high-risk patients.

CONCLUSIONS

This proof-of-principle study confirms that AFI can be used as a red-flag technique to detect suspicious lesions. With NBI, detailed inspection of the surface patterns can be performed. This combination may increase the accuracy of detecting HGIN in BE.

Ultraviolet-induced autofluorescence characterization of normal and tumoral esophageal epithelium cells with quantitation of NAD(P)H

Cellular autofluorescence was characterized in normal human esophageal cells and in malignant esophageal epithelial cells. The study was performed under excitation at 351 nm where the cell fluorescence is mainly due to the reduced pyridine nucleotides (NAD(P)H) with a very small contribution from the oxidized flavins (FMN, FAD) or lipopigments. The autofluorescence emission of squamous cell carcinoma, adenocarcinoma on Barrett's mucosa and normal cells was characterized by microspectrofluorimetry on monolayers and by spectrofluorimetry on cell suspensions. The relative contribution of each fluorophore to the fluorescence emission of the different cell types was evaluated by a curve-fitting analysis. A statistically highly significant difference was observed between the average intensity of the raw spectra of the different cell types. Tumoral cells had a fluorescence intensity approximately twice as high as that of normal cells. The results of the NAD(P)H quantitation analyzed by microspectrofluorimetry on single living cells and spectrofluorimetry on cell suspensions were consistent with those obtained by biochemical cycling assays, showing that the amount of intracellular NAD(P)H is higher in tumoral cells than in normal cells. Bound NAD(P)H concentration was found to be quite stable whatever the cell type while the amount of free NAD(P)H showed a very important increase in tumoral cells.

Spectroscopy and fluorescence in esophageal diseases

Malignant tumors of the esophagus continue to be a major health issue associated with high mortality primarily because most present with symptoms of dysphagia or anaemia. The disease at that stage is advanced and not likely curable. The big issue for squamous dysplasia and that associated with BE is that only a small proportion are discovered in surveillance programs when they are asymptomatic, either because the patient lives in a high-incidence geographical area, has a family history, previously diagnosed head and neck cancer or chronic reflux, as in Barrett's. Current endoscopic methods are hampered by the endoscopist's inability to recognize subtle topographic clues of dysplasia, sampling errors related to biopsy protocols, and confounding inflammation-induced artifacts both for the endoscopist and pathologist. What is desperately needed would be a biomarker (e.g. serological, fecal, urinary) that selects patients for endoscopy. However, such a test is not yet on the horizon. This article examines the current status in practice and research of novel optically based 'bioendoscopic' devices (i.e. fluorescence spectroscopy and imaging, confocal fluorescence microendoscopy (CFM), light scattering spectroscopy (LSS), Raman spectroscopy (RS), and immunophotodiagnostic endoscopy) which may enhance the diagnosis of dysplasia in all patients undergoing conventional white light endoscopy. Perhaps these new technologies will lead to more cost-effective diagnosis, mapping (e.g. surface), and staging (e.g. depth) of dysplasia, thereby allowing timely cure by endoscopic means (e.g. EMR and/or PDT), biological interventions (e.g. Cox-2 inhibitors) rather than esophajectomy.

Técnicas endoscópicas emergentes. La llegada de la histología virtual

Endoscopic technology has evolved in such a way that gastroenterologists can now visualize and store high-resolution images of the gastrointestinal tract. This has improved the approach to precancerous and cancerous lesions of the gastrointestinal tract and biliary tree. However, certain difficulties remain, especially in relation to diagnosis. In the last few years, multiple techniques have been developed that, using the properties of light, enable an instantaneous histologic diagnosis to be made while endoscopy is being performed. What has been called the "optical biopsy" allows highly exact information to be obtained, both from the morphological and functional point of view. Some of these techniques, such as chromoendoscopy and magnification, are already being performed in clinical practice while others are still under investigation. The aim of the present article is to review the underlying principles and applications of these emerging techniques.

Endoscopic detection of early upper GI cancers

The detection of early-stage neoplastic lesions in the upper GI tract is associated with improved survival and the potential for complete endoscopic resection that is minimally invasive and less morbid than surgery. Despite technological advances in standard white-light endoscopy, the ability of the endoscopist to reliably detect dysplastic and early cancerous changes in the upper GI tract remains limited. In conditions such as Barrett's oesophagus, practice guidelines recommend periodic endoscopic surveillance with multiple biopsies, a methodology that is hindered by random sampling error, inconsistent histopathological interpretation, and delay in diagnosis. Early detection may be enhanced by several promising diagnostic modalities such as chromoendoscopy, magnification endoscopy, and optical spectroscopic/imaging techniques, as these modalities offer the potential to identify in real-time lesions that are inconspicuous under conventional endoscopy. The combination of novel diagnostic techniques and local endoscopic therapies will provide the endoscopist with much needed tools that can considerably enhance the detection and management of early stage lesions in the upper GI tract.

Optical biopsy: a new frontier in endoscopic detection and diagnosis

Endoscopic diagnosis currently relies on the ability of the operator to visualize abnormal patterns in the image created by light reflected from the mucosal surface of the gastrointestinal tract. Advances in fiber optics, light sources, detectors, and molecular biology have led to the development of several novel methods for tissue evaluation in situ. The term "optical biopsy" refers to methods that use the properties of light to enable the operator to make an instant diagnosis at endoscopy, previously possible only by using histological or cytological analysis. Promising imaging techniques include fluorescence endoscopy, optical coherence tomography, confocal microendoscopy, and molecular imaging. Point detection schemes under development include light scattering and Raman spectroscopy. Such advanced diagnostic methods go beyond standard endoscopic techniques by offering improved image resolution, contrast, and tissue penetration and providing biochemical and molecular information about mucosal disease. This review describes the basic biophysics of light-tissue interactions, assesses the strengths and weaknesses of each method, and examines clinical and preclinical evidence for each approach.

Endoscopic fluorescence spectroscopic imaging in the gastrointestinal tract

Fluorescence detection is one of a series of new optical biopsy techniques that have been adapted and evaluated for implementation in gastrointestinal endoscopy. Endogenous fluorescence enables the detection of metabolic and structural changes in human tissue and thus may offer information for the detection of early stage dysplastic and malignant lesions of the mucosa that remain invisible in white light endoscopy. Tissue fluorescence can be detected by point-spectroscopic sampling of the mucosa or by processing the fluorescence information to generate an endoscopic image. Different approaches have been evaluated in pilot studies, and the results in terms of high diagnostic sensitivity and specificity are encouraging. However, large multi-center trials are necessary to evaluate the accuracy and predictability of these new optical tools for the endoscopic diagnosis of early cancerous lesions in the gastrointestinal tract.

The combined use of fluorescence, reflectance, and light-scattering spectroscopy for evaluating dysplasia in Barrett's esophagus

Intrinsic fluorescence, diffuse reflectance, and light-scattering spectroscopy provide complementary information on biochemical and morphologic information extending potentially from the molecular to the tissue level. Model-based spectral analysis in each case yields results about specific tissue parameters in a quantitative manner.Preliminary studies demonstrate that these parameters can be used for the development of algorithms that can detect dysplastic changes in patients with Barrett's esophagus (BE) with high sensitivity and specificity. Studies validating tri-modal spectroscopy based algorithms and real-time spectroscopic data analysis are under way to provide a more accurate and extensive assessment of the potential of this approach as a clinical noninvasive tool that could improve the management and treatment of BE dysplasia.

Photodynamic therapy with green light and m-tetrahydroxyphenyl chlorin for intramucosal adenocarcinoma and high-grade dysplasia in Barrett's esophagus

BACKGROUND

The eradication of early stage neoplastic lesions in Barrett's esophagus is imperative to prevent invasive adenocarcinoma. Early stage lesions have an extremely low risk of lymph node metastasis, thereby, making local treatment feasible. Photodynamic therapy destroys malignant cells by a photochemical effect. The aims of this study were to evaluate the efficacy and tolerance of photodynamic therapy with green light and a new photosensitizer, temoporfin or m-tetrahydroxyphenyl chlorin in patients with Barrett's esophagus and early stage neoplastic lesions.

METHODS

Four days after injection of m-tetrahydroxyphenyl chlorin, lesions were illuminated at a wavelength of 514 nm through non-circumferential windowed diffusers. Follow-up endoscopy with biopsies was performed at regular intervals.

RESULTS

Fourteen lesions (7 high-grade dysplasia, 7 intramucosal adenocarcinoma) in 12 patients were treated. For all lesions, efficacy was 100% and squamous re-epithelialization was complete. Side effects were of moderate severity (one stricture). Mean follow-up was 34 (15) months (range 12-68 months).

CONCLUSIONS

Green light photodynamic therapy with m-tetrahydroxyphenyl chlorin can eradicate early stage neoplastic lesions in Barrett's esophagus and may be proposed as an alternative first-line therapy or a second-line therapy after failure of other endoscopic treatments. The efficacy and patient tolerance of the procedure justify further studies of the method in larger groups of patients.

Optical detection and eradication of dysplastic Barrett's esophagus

Dysplastic Barrett's esophagus is a condition that offers multiple diagnostic and therapeutic challenges. The diagnosis of dysplasia within Barrett's esophagus currently relies on periodic endoscopic surveillance with multiple biopsies, a methodology limited by random sampling error, inconsistent histopathologic interpretation and delay in diagnosis. Optical spectroscopic and imaging techniques have the potential to identify dysplastic or early neoplastic lesions in real-time. These diagnostic modalities are needed to enhance the endoscopic surveillance of Barrett's esophagus in the future as well as help to define lesions for endoscopic therapy. Esophagectomy has been the standard of care for Barrett's esophagus with high-grade dysplasia although it is a procedure associated with significant morbidity and mortality. Minimally invasive endoscopic ablative therapies are attractive and less morbid alternatives to esophagectomy, with promising results obtained from the use of light-activated drugs (i.e., photodynamic therapy). The combination of novel optical diagnostic techniques and therapies will provide the endoscopist with much needed tools that can considerably enhance the management of patients with Barrett's esophagus. This article reviews the current status and future prospects of optical-based modalities for diagnosis and therapy of dysplastic Barrett's esophagus.

Fluorescence and Raman spectroscopy

Table 2 provides a summary of selected in vivo fluorescence and Raman studies performed in BE. Although the findings from these studies appear promising, these techniques are still under development, and it is anticipated that technological refinements will further enhance their diagnostic accuracy. Ultimately, however, large-scale prospective clinical trials are required to determine their true diagnostic potential in BE and other sites. Ideally, the instrumentation of choice would be a real-time endoscopic system that combines excellent diagnostic accuracy with wide-area sampling. In this regard, fluorescence imaging is most appealing, although a variety of issues remain to be resolved, including the choice between autofluorescence versus drug-induced fluorescence and the problematic distinction between dysplastic (true positive) and confounding background metaplastic fluorescence (false positive), among others. It is also not clear whether exogenous fluorophores are necessary to achieve clinically useful sensitivity and specificity for lesion detection in BE. Point spectroscopic techniques, either fluorescence or Raman scattering, are inherently limited by the small volume of tissue (biopsy specimen size) they sample, but more detailed information can be extracted from the spectra, which may increase diagnostic accuracy. Moreover, it may be that the optimal system will be a combination of multiple optical spectroscopic or imaging techniques (multimodality approach), as suggested by Georgakoudi et al. For instance, a lesion could be detected by fluorescence imaging and its dysplastic nature characterized (graded) by Raman spectroscopy. In this era of cost containment, however, the critical challenge is to demonstrate whether an increase in diagnostic accuracy merits investment in costly technology, regardless of the technique used.

Endoscopy in Barrett's esophagus. Surveillance during reflux management and new advances in the diagnosis and early detection of dysplasia

Given the alarming rise in the incidence of esophageal cancer and the fact that Barrett's esophagus is clearly a precursor to this disease, effective surveillance is desirable. Endoscopic surveillance is recommended by major endoscopic and gastrointestinal societies based on the available data and hypothetic models suggest that the costs of endoscopic surveillance for Barrett's esophagus may be reasonable when compared with other commonly applied cancer screening strategies. Although, however, most implicated physicians agree that surveillance is warranted, recommended guidelines often are not followed. This occurrence may reflect the importance of some of the practical limitations inherent to carrying out intensive endoscopic biopsy protocols in large numbers of eligible patients. In an effort to improve the surveillance process, several new techniques have been tested and are in development. These techniques are aimed at facilitating the histologic sampling of larger areas of metaplastic epithelium, at better targeting sites more likely to harbor dysplasia and cancer, and at replacing endoscopic biopsies with nonhistologic tissue analysis. Although many of these newer techniques are promising, however, none are currently close to widespread clinical application. The current standard for surveillance remains the use of systematic endoscopic biopsies, with the frequency of surveillance endoscopies determined by the severity of any dysplastic changes that are found. Given the large number of patients that are likely to be eligible for screening and the current constraints in terms of physician availability and health-care resources, endoscopic biopsy will remain the cornerstone of Barrett's esophagus surveillance strategies unless newer alternatives are clearly advantageous in terms of accuracy, cost, availability, and ease of application. In the future, however, advances in techniques for minimally invasive ablation of Barrett's epithelium may make endoscopic surveillance obsolete altogether.