PHOTODYNAMIC THERAPY USING INTRAVENOUS DELTA-AMINOLEVULINIC ACID-INDUCED PROTOPORPHYRIN-IX SENSITIZATION IN EXPERIMENTAL HEPATIC-TUMORS IN RATS

The efficacy of photodynamic therapy (PDT) using delta-aminolaevulinic acid (ALA)-induced protoporphyrin M. (PpIX) sensitisation and laser l ight at 635 nm was investigated in the treatment of experimental hepat ic tumours. The model of liver tumours was induced either by local ino culation or by administration of tumour cells through the portal vein in rats. ALA at a dose of 60 mg kg(-1) b.w. was intravenously administ ered 60 min before PDT. PpIX accumulation in tumour, normal liver and abdominal wall muscle was detected by means of laser-induced fluoresce nce (LIF). Laser Doppler imaging (LDI) was used to determine changes i n the superficial blood how in connection with PDT. Histopathological examinations were performed to evaluate the PDT effects on the tumour and the surrounding liver tissue, including pathological features in t he microvascular system. The accumulation of PpIX, as monitored by LIF , showed high fluorescence intensities at about 635 nm in both the hep atic tumour tissue and normal liver and low values in the abdominal wa ll. LDI demonstrated that the blood how in the treated tumour and its surrounding normal liver tissue decreased immediately after the PDT, i ndicating an effect on the vascular system. A large number of thrombi in the irradiated tumour were found microscopically 3 h after the PDT. The tumour growth rate showed a marked decrease when evaluated 3 and 6 days after the treatment. These results show that the ALA-PDT is eff ective in the inhibition of growth of experimental hepatic tumours.