PHOTODYNAMIC THERAPY OF ORAL-CANCER - PHOTOSENSITIZATION WITH SYSTEMIC AMINOLEVULINIC ACID

Photodynamic therapy with intravenous photosensitising drugs has been shown to be effective in the ablation of superficial cancers, but long -lasting photosensitivity is a serious disadvantage. Similar photosens itivity is a feature of certain types of porphyria. We present the fir st report of tumour necrosis brought about by photodynamic activation of a temporary endogenous porphyrin accumulation, after an oral dose o f the haem precursor, 5-aminolaevulinic acid. In 4 patients, quantitat ive fluorescence microscopy showed that accumulation of the photoactiv e intermediate protoporphyrin IX peaked after 4-6 h in 4 oral cavity s quamous cell carcinomas, returning to background in 24 h. Irradiation with non-thermal red laser light caused tumour necrosis in 3 patients.