Photodetection of cervical intraepithelial neoplasia using 5-aminolevulinic acid-induced porphyrin fluorescence

BACKGROUND. Screening for cervical carcinoma and its precursors is based on cervical cytology and diagnostic colposcopy. Despite the decrease in the i ncidence of cervical carcinoma in countries with a good screening program, this rate of decline is leveling off. Known problems are false-negative rat es of cytology and low specificity of colposcopy. This clinical study exami ned the diagnostic potential of porphyrin fluorescence in patients with cer vical intraepithelial neoplasia Grade 1-3 (CIN 1-3). METHODS. Sixty-eight women attending our colposcopy clinic underwent a gyne cologic examination, including cytology, human papillomavirus (HPV) testing , and colposcopy, They received 10 mt 0.5% or 1.0% 5-aminolevulinic acid (5 -ALA) topically. After 30-360 minutes, real-time image analysis was perform ed, and spectra were obtained from 685 sites. RESULTS. Due to rapid photobleaching, 0.5% 5-ALA proved ineffective for flu orescence assessment. Using 1% 5-ALA, the authors found that fluorescence i ntensities correlated with incubation time; however, fluorescence contrast showed a maximum at 60-90 minutes (ratio 11:1). HPV DNA positive lesions sh owed significantly higher fluorescence. Fluorescence imaging after 60-90 mi nutes achieved similar sensitivity and specificity compared with colposcopy in detecting CIN with 94% and 51% Versus 95% and 50%, respectively. Howeve r, the specificity was markedly improved by fluorescence spectroscopy, achi eving 75%. The evaluation of spectral measurements revealed significantly h igher values for CIN compared with normal tissue and for CIN 2/3 compared w ith CIN 1 (P < 0.001). CONCLUSIONS. Using a time interval of 60-90 minutes after topical applicati on of 1% 5-ALA, the authors observed specific porphyrin fluorescence of GIN . Fluorescence spectroscopy promises to become a valuable tool for the diag nosis of GIN. Cancer 2000;88:2275-82, (C) 2000 American Cancer Society.