CHAPTER 20: Photodynamic Medicine in Neurosurgery: Biochemical, Technical and Clinical Aspects

Malignant brain tumours carry a lethal prognosis with a median survival of 15 months for grade IV tumours and are not curable by surgery or other adjuvant therapies due to their heterogeneity and invasion into normal brain structures. Photodynamic techniques such as photodynamic diagnosis (PDD), fluorescence-guided tumour resection (FGR) and photodynamic therapy (PDT) are currently undergoing intensive clinical investigations as adjunctive treatments for malignant brain tumours in order to achieve the fourth mainstay therapy in neuro-oncology besides surgery, chemotherapy and radiotherapy. Whereas FGR is already considered the gold standard for the resection of brain tumours, PDT is still not widely acknowledged as a therapeutic option. Despite various treatment protocols and variation of photosensitisers and light dose, there is a clear trend towards prolonging median survival after one single PDT as compared to conventional therapeutic modalities. According to a meta-analysis, the median survival after PDT for primary WHO grade IV glioblastoma multiforme (GBM) was 22 months and for recurrent GBM was 9 months as compared to standard conventional treatment survival times of 15 and 3 months, respectively. Furthermore, PDT significantly improved the quality of survival and delayed tumour relapse (p < 0.001). Fluorescence-guided surgical resection significantly reduced tumour burden by 35–70% and the combination of PDD/FGR and intra-operative PDT (“to see and to treat”) offers an exciting and logical approach to treating malignant brain tumours. PDT was generally well tolerated and its side effects consisted of occasionally increased intracranial pressure and prolonged skin sensitivity to direct sunlight. This review is an up-to-date overview of the clinical data for PDT, photosensitisers, technical developments and indications for photodynamic applications in neurosurgery.