Primary Motility  Disorders of the  Esophagus
 The Esophageal
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 Barrett's
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OESO©2015
 
Volume: Barrett's Esophagus
Chapter: Dysplasia
 

Do the newest laser induced fluorescence techniques allow for a quick screening of the entire Barrett's mucosa? What is the cost of such equipment?

G.N.J. Tytgat (Amsterdam)

Endoscopic identification of dysplasia is notoriously difficult. Dysplasia can usually not be distinguished endoscopically from non-dysplastic adjacent mucosa. Detection and surveillance of dysplasia therefore largely depends on random-biopsy and the skills of the individual endoscopist to discern subtle mucosal abnormalities.

New optical methods are being developed for reliable real-time detection of dysplasia such as optical coherence tomography, raman spectroscopy, elastic scattering spectroscopy, and fluorescence spectroscopy. They all exploit microarchitectural and biochemical changes in tissue. Each technique has its own special features and specific application.

Tissue autofluorescence

All tissues exhibit endogenous fluorescence (autofluorescence) if exposed to light of a certain wavelength. Irradiation of fluorophores by light can lead to excitation and subsequent fluorescence emission. Excitation is caused by absorption of the incident radiation by a fluorophore, causing electrons to be raised to a higher energy state. Subsequent relaxation leads to the emission of fluorescent light. The wavelength of the emitted fluorescent light is longer than the wave length of the excitation light. This difference in wavelength between excitation and emitted fluorescent light can be detected. Amongst the fluorophores are the co-enzymes in the oxidation-reduction reactions: the pyridine nucleotides NADH and NADPH, and the flavins such as FADH2 and FMNH. Metabolism activation causes a shift to oxidized forms (NAD+, NADP+, FMN+, FAD+) which then leads to reduction in fluorescence. Other important tissue fluorophores include connective-tissue proteins collagen and elastin, as well as intermediates of the heme synthesis as porphyrin. Different excitation wavelengths activate different fluorophores. A typical endogenous fluorescent spectrum of colonic dysplasia at excitation around 400 nm differs from the surrounding normal mucosa in that the green fluorescence intensity is significantly lower, especially around 550 nm, whereas red fluorescence is increased. This difference is thought to be secondary not only to fluorophore composition, but also to differences in tissue microarchitecture, as well as differences in absorption.

Laser-induced tissue fluorescence spectroscopy

The first gastrointestinal Laser-Induced Fluorescence Spectroscopy (LIFS) study was performed by Kapadia et al. in 1990 [1]. In an ex vivo study the authors were able to discriminate 16 colon adenomas from hyperplastic polyps with a sensitivity and specificity of 100% and 94% respectively. Shomacker confirmed the ability of LIFS to differentiate between neoplastic and non-neoplastic tissue with a sensitivity and specificity of 80 and 92% [2]. In the earliest in vivo study by Cothren in 1990, colon adenomas could be distinguished from the surrounding mucosa in 97% of cases [3]. The first LIFS study in the esophagus was done by Panjehpour et al. in 32 patients with known esophageal carcinoma [4]. In a later study, the same group has successfully identified all 7 patients with highgrade dysplasia, but none of the 6 patients with low-grade dysplasia, in a series of 36 patients with Barrett's esophagus [5].

However, as was pointed out by Van Dam et al. in an accompanying editorial, optical sampling of large areas of mucosa with LIFS is cumbersome and sampling can only be targeted towards endoscopically visible lesions [6].

Light-induced fluorescence endoscopy

A real-time fluorescence imaging system, incorporated in a standard endoscope, enables screening of large surface areas and allows for targeted biopsy sampling. Using such realtime imaging instrument (LIFE-GI), dysplastic lesions occult to detection with white light could be visualized. Du Vall et al. were able to identify two high-grade dysplastic lesions occult to standard endoscopy in a series of 102 patients [7]. The overall sensitivity and specificity for dysplasia in this series reached 85 and 81% when biopsy samples from Barrett were excluded. Other investigators evaluating the LIFE-GI system were able to recognize 24 dysplastic lesions in the stomach with a sensitivity of 96%, in a series which included 18 early gastric cancers [8]. In a series of 59 gastric cancers, Yano et al. reported detection of the lesions with a sensitivity of 88%. This study included one early gastric cancer occult to standard endoscopy [9].

Exogenous fluorescence imaging

The low intensity of the fluorescence signal, and artefacts caused by scattering and fluorescence re-absorption, renders detection and interpretation of the autofluorescence complicated. Inflammatory processes in particular can interfere with the fluorescence patterns mimicking those of dysplasia. Exogenous fluorophores specifically retained in neoplastic tissue may improve the discriminating potential of fluorescence imaging. Bjorkman [10] evaluated hematoporphyrin derivative (HPD) to identify malignancy in the rate colon and was able to enhance the diagnostic sensitivity and specificity of HPD fluorescence for carcinoma to 95% and 98%. Stael von Holstein et al. [11] successfully used HPD induced fluorescence in Barrett's esophagus and esophageal adenocarcinoma both in vitro and in vivo. Dets et al. used Hypercin® induced fluorescence to detect gastric cancer [12]. Messmann et al. used 5-aminolevulinic acid (ALA) induced protoporphyrin IX (PpIX) fluorescence to detect dysplasia in a rat colitis model [13]. A narrow-band blue-light source (395-436 nm) was used for fluorescence excitation. Tissue fluorescence was detected without any sophisticated signal intensifying equipment. With a dose of 75 mg/kg of ALA dysplasia was identified with a sensitivity of 92%. Specificity and positive predictive value however, were only 35% and 40% respectively. Inflammation appeared to be a major pitfall and disturbing factor. The same authors also evaluated tissue sensitization with 5ALA, which leads to accumulation of protoporphyrin IX and induction of red fluorescence in Barrett's patients. In a pilot study of 6 patients, dysplasia was found exclusively in areas of red fluorescence [14]. Instead of random biopsies, targeted biopsy specimens of potential dysplastic lesions can thus be obtained [15].

Concluding remarks

Over the next decade spectroscopic techniques may expand the capabilities of gastrointestinal endoscopy. Clinical application of fluorescence detection of dysplasia and early cancer is still in its infancy. LIF spectroscopy and LIF endoscopy provide the endoscopist with a real-time, accurate, non-invasive technique for detection of dysplasia and early cancer. Detecting lesions occult to standard white-light endoscopy appears possible. Whether this technique can correctly detect dysplasia in the presence of active inflammation remains to be seen. Large scale studies are currently ongoing evaluating the diagnostic yield of fluorescence techniques in screening for gastrointestinal malignancy. Future studies may validate fluorescence endoscopy which would render fluorescence guided biopsies a valuable method for detection of dysplasia and cancer.

References

1. Kapadia CR, Cutruzzola FW, O'Brien KM, Stetz M, Enriquez R, Deckelbaum L. Laser-induced fluorescence spectroscopy of human colonic mucosa. Detection of adenomatous transformation. Gastroenterology 1990;99:150-157.

2. Shomacker KT, Frisoli JK, Compton CC, Flotte TJ. Ultraviolet laser-induced fluorescence of colonic tissue:basic biology and diagnostic potential. Lasers Surg Med 1992;12:63-78.

3. Cothren RM, Richards-Kortum R, Sivak MV, van Dam J, Petras RE, Fitzmaurice M, et al. Gastrointestinal tissue diagnosis by laser induced fluorescence spectroscopy at endoscopy. Gastrointest Endosc 1990;36:105-111.

4. Panjehpour M, Overholt BF, Schmidhammer JL, Farris C, Buckley PP, Vo-Dinh T. Spectroscopic diagnosis of esophageal cancer:new classification model, improved measurement system. Gastrointest Endosc 1995;41:577-581.

5. Panjehpour M, Overholt BF, Vo-Dinh T, Haggitt RC, Edwards DH, Buckley PF. Endoscopic fluorescence detection of high-grade dysplasia in Barrett's esophagus. Gastroenterology 1996;111:93-101.

6. van Dam J, Bjorkman DJ. Shedding some light on high-grade dysplasia. Gastroenterology 1996;111:247-249.

7. DuVall A, Wilson BC, Marcon N. Light induced fluorescence endoscopy. In: Cotton PB, Tytgat GNJ, Williams CB, Bowling TE, eds. Annual of Gastrointestinal Endoscopy, 10th edition. London:Rapid Science Publishers, 1997:25-30.

8. Namihisa A, Watanabe H, Tanaka H, Miwa H, Ogihara T, Sato N. Detection of gastric lesions by endoscopic autofluorescence real time imaging system (Light Induced Fluorescence Endoscopy). Gastroenterology 1997;112.

9. Yano H, Iishi H, Tatsuta M. Diagnosis of gastric cancer by endoscopic autofluorescence imaging system. Endoscopy 1997;29:E21.

10. Bjorkman DJ, Samowitz WS, Brigham EJ, et al. Fluorescence localization of early colonic cancer in the rat by hematoporphyrin derivate. Lasers Surg Med 1991;11:263-270.

11. Stael von Holstein C, Nilsson AMK, Andersson-Engels S, Willen R, Walther B, Svanberg K. Detection of adenocarcinoma in Barrett oesophagus by means of laser induced fluorescence. Gut 1996;39:711-716.

12. Dets SM, Buryi AN, Melnik IS, Joffe AY, Rusina TV. Laser-induced fluorescence detection of stomach cancer using hypercin. SPIE Optical Biopsies and Microscopic Techniques 1996;2926:51-56.

13. Messmann H, Kullmann P, Knuchel-Clarke R, Wild T, Ruschoff J, Gross J, et al. Fluorescence detection of dysplastic lesions in a rat colitis model after prior 5-aminolevulinic acid photosensitation. Endoscopy 1998;30.

14. Messmann H, Knuchel R, Baumler W, et al. Endoscopic fluorescence detection of dysplasia in patients with Barrett's esophagus, ulcerative colitis, or adenomatous polyps after 5-aminolevulinic acid-induced protoporphyrin IX sensitization. Gastrointest Endosc 1999;49:97-101.

15. Haringsma J, Tytgat GNJ. Detection of dysplasia in Barrett's esophagus using light-induced fluorescence endoscopy. Endoscopy 1997;29:S35.


Publication date: August 2003 OESO©2015