Evaluation of ALA-PDT of ovarian cancer in the Fisher 344 rat tumor model

Summary 

Objective

This study aimed to evaluate aminolevulinic acid-photodynamic therapy (ALA-PDT) in an experimental tumor model to expand the use of PDT in the treatment of ovarian cancer with peritoneal carcinosis.

Materials and methods

5-Aminolevulinic acid (ALA) (Photocure ASA, Norway) 60mg/kg was injected in the peritoneum cavity of 45 female rats Fisher with induced peritoneal metastases of ovarian cancer. ALA-PDT was performed 4h later with two different lasers: (1) laser diode (Diomed, Cambridge, UK), at 630nm, 100mW/cm², or (2) KTP laser (Laser Quantum, Stockport, UK), 532nm, 30mW/cm². The animals were divided into five groups: LASER ALONE group, CTRL group (no cancer), NO LASER group, 1 DOSE group (PDT during 1s) and 1.5 DOSE group (PDT during 1.5s). Biopsies were taken 24h after treatment. A semi-quantitative score called necrosis value (NV) was assigned to each sample that reflected the depth of the peritoneal necrosis.

Results

In the first two groups, the peritoneum remained intact irrespective of the wavelength. In the 1 DOSE group, necrosis was observed for 532nm and 630nm. In the 1.5 DOSE group, necrosis was observed for 532nm (NV: 3.22±0.83) and 630nm (NV: 2.67±1.00) (p<0.05). The mesothelium strongly thinned out in the diffuse shape of the tumor.

Conclusion

Only ALA-PDT induces tumor necrosis with either 532nm and 630nm and should be considered an effective therapy for micrometastasis of ovarian cancer. This preliminary study deserves further experiments.

Keywords: Photodynamic therapy, 5-Aminolevulinic acid, Protoporphyrin IX, Ovarian cancer, 532-nm Laser, 630-nm Laser