Photodynamic therapy of brain tumours.

Photodynamic therapy is a binary treatment combining the selective uptake of a photosensitizer into a tumour followed by irradiation of the tumour with light of the appropriate wavelength to cause activation of the sensitizer as selective tumour kill. Photodynamic therapy has been extensively investigated in laboratory studies in the treatment of cerebral tumours and has been utilised in clinical trials to treat a variety of tumours including cerebral glioma. The clinical trials have usually used PDT as an adjuvant therapy following tumour resection but studies are being undertaken to use the treatment in combination with stereotactic techniques. The photosensitizer haematoporphyrin derivative (HpD) has been shown to be selectively localised into all grades of glioma with a direct correlation between the grade of glioma and HpD level in the tumour. The levels were highest in the glioblastoma multiforme (mean uptake of 5.9 micrograms HpD/g tumour wet weight) and lower in the intermediate grade anaplastic astrocytoma (2.4 micrograms/g) and low grade astrocytoma (1.6 micrograms/g). Uptake into normal brain tissue taken from HpD sensitized patients was 0.2 microgram/g. HpD was also localised into the brain adjacent to the tumour region.