Fluorescence endoscopy for the detection of dysplasia in ulcerative colitis using systemic or local 5-aminolevulinic acid sensitisation

E. Endlicher, G. Freunek, P. Rümmele 1, J. Schölmerich, R. Knüchel, H. Messmann

Internal Medicine I, 1Institute of Pathology, University of Regensburg, Germany

Background and Aim: Longstanding ulcerative colitis, especially in the presence of dysplasia, is associated with an increased risk of developing cancer. Since dysplasia are not visible during routine endoscopy, random biopsies in four quadrants every 10 cm are recommended. Fluorescence endoscopy after sensitisation with 5-aminolaevulinic acid (5-ALA) was assessed for optimal sensitisation mode and dose in order to visualize or exclude dysplasia in ulcerative colitis. 5-ALA is converted intracellularly into protoporphyrin IX which accumulates selectively in neoplastic tissue and can be detected by typical red fluorescence after illumination with blue light. Methods: In fourty eight patients with ulcerative colitis seventy one examinations were performed with fluorescence endoscopy after oral (20 mg/kg) or local (either with an enema (2g and 3g ALA) or by spraying the mucosa with a catheter) sensitisation with 5-ALA. A total of 668 biopsies of red fluorescent (n=301) and non-fluorescent (n=367) areas of the colonic mucosa were taken. Results: 47 biopsies in 14 patients revealed dysplasia. Sensitivity of fluorescence endoscopy to detect dysplasia ranged from 87%-100% after local sensitisation, in contrast to only 43% after systemic administration. Specificity did not differ for all forms of local sensitisation (enema 51% and 57% for 3g and 2g ALA, respectively and spray-catheter 62%), after systemic sensitisation specificity was 73%. Negative predictive values of non-fluorescent mucosa for the exclusion of dysplasia were 89% after systemic sensitisation and 98-100% after local sensitisation. Conclusion: Fluorescence endoscopy after 5-ALA sensitisation, especially after local administration, may be able to detect or exclude dysplasia in ulcerative colitis.

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Paper presented at the International Symposium on Predictive Oncology and Intervention Strategies; Paris, France; February 9 - 12, 2002; in the section on Risk Assessment, Part 1.