Comparison of continuous and fractionated illumination during hexaminolaevulinate-photodynamic therapy

Summary 

Objective

This experimental study aimed to compare continuous and fractionated illumination to optimize hexaminolaevulinate (HAL)-photodynamic therapy (PDT) in a rat tumour model with advanced ovarian cancer.

Materials and methods

Intraperitoneal 10⁶ NuTu-19 cells were injected in 36 female rats Fisher 344. Peritoneal carcinomatosis was obtained 26 days post-tumour induction. Four hours post-intraperitoneal HAL (Photocure ASA, Oslo, Norway) injection, two schemes of PDT were performed at 30mWcm⁻² on a 1cm² area: fractionated illumination (n=16) with a on–off cycle (“on”: 2min and “off”: 1min) until a fluence of 30Jcm⁻² was delivered, and continuous illumination (n=20) with a fluence of 45Jcm⁻². Laser light was generated using a 532nm KTP laser (Laser Quantum, Stockport, UK). Biopsies were taken 24h after treatment. Semi-quantitative histology was performed. Necrosis value was determined—0: no necrosis to 4: full necrosis.

Results

HAL-PDT was efficient in producing necrosis irrespective of the scheme (NV=3.34±0.91). Tumour destruction was superior with fractionated illumination compared to continuous illumination (3.67±0.70 vs. 3.10±0.94) (p<0.05).

Conclusion

Fractionated illumination during photodynamic therapy was shown to improve tumour response. Fractionated illumination with short intervals should be considered for an effective PDT of advanced ovarian cancer.

Keywords: Photodynamic therapy, Hexaminolaevulinate, Fractionated, Ovarian cancer, Protoporphyrin IX