Benefits and Problems of Photodynamic Diagnosis in Brain Tumor Treatment

Maximum and safe removal of malignant gliomas is no easy, and various modalities are used, including photodynamic diagnosis (PDD) using 5-aminolevulinic acid (5-ALA). Fluorescence guided surgery (Fluorescence Guided Surgery: FGS) using 5-ALA is highly useful for malignant gliomas, because it selectively accumulates in the tumor cells and the presence of the tumor cells can be demonstrated in a very simple and real-time manner by the assessment of emitting fluorescence of its metabolite Protoporphyrin IX (PpIX). Recently, the mechanism of PpIX accumulation has been elucidated, and in the future, research to increase the effects of PDD and PDT by increasing the efficiency of accumulation is expected. On the other hand, 5-ALA PDD is not useful in lower-grade gliomas due to problems including false positives and false negatives, and its use requires sufficient knowledge and experience. In order to overcome these problems, PpIX fluorescence quantification using spectral analysis have been developed, and further development of these techniques is expected. Recently, it was shown that PDD is possible using talaporfin sodium, which has been approved as a photodynamic therapy (PDT) treatment in Japan, and more effective surgical treatment will be developed by combining PDD and PDT using talaporfin sodium in the future.