QUANTITATIVE STUDIES OF THE KINETICS OF 5-AMINOLEVULINIC ACID-INDUCEDFLUORESCENCE IN BLADDER TRANSITIONAL-CELL CARCINOMA

Photodynamic therapy is a potential treatment for superficial bladder cancer that utilizes photosensitizer drugs, which are activated by lig ht to cause tissue destruction. However, first-generation photosensiti zers cause prolonged phototoxicity, have poor tumour specificity and c an accumulate within detrusor muscle, resulting in permanent loss of b ladder capacity following treatment. A newer drug, called 5-aminolaevu linic acid (ALA), generates a sensitizer called protoporphyrin IX (PpI X) in situ and has been shown, qualitatively, to be more tumour specif ic. The fluorescence kinetics of ALA-induced PpIX was investigated in patient biopsies of bladder tumour, normal urothelium and detrusor mus cle, both in vitro after incubation of specimens in ALA-rich culture m edium for Various times and in vivo after instillation of intravesical ALA before endoscopic resection. The fluorescence in tumour tissue wa s twice that of normal urothelium in vitro and up to tenfold in vivo. There was little ALA-induced fluorescence in detrusor muscle, both in vitro and in vivo. Most importantly, no patients experienced phototoxi city or other adverse events following intravesical instillation of AL A.