What provides for the best conformal PDT treatment in intracranial neoplasm

Applying photodynamic therapy as local photochemical therapy to neoplasm is facing two contradictory requirements, first maximizing the cytotoxic dose in the brain adjacent to tumour in order to achieve a larger than 99% resection required to provide a significant survival advantage and second limiting the cytotoxic dose to avoid undue neuronal damage resulting in neurological deficits. Current work in the biophotonics group in Toronto focuses on all approaches to improve the selectivity of the cytotoxic dose resulting from PDT therapy, through investigating novel photosensitizers, confining the light source based on improved treatment planning and developing strategies to modify the biological response of tumour cells versus neurons for a given cytotoxic dose. All three approaches will have to be combined due to the need to maintain cell kill selectivity over 20 mm in depth or more than 3 light penetration depth at 635 nm a commonly used wavelength for PDT. The main strategies to achieve a modification of the tissue response pertain to evaluating type I based photosensitizer and various approaches for neuroprotection.