2014 年 21 巻 3 号 p. 14-21
Malignant glioma is extremely difficult to treat because of its invasiveness and obscure borders between the tumor and surrounding brain, which are due to a mixture of tumor cells and nerve tissue in the area around the tumor. For surgical removal of malignant glioma, it is important to at least confirm the area of the main mass which is rich in tumor cells. Many methods including frozen section during operation, pre- and intra-operative imaging diagnosis, and navigation system are used for this purpose. Photodynamic diagnosis or photodynamic detection (PDD) is a method that uses various fluorescent dyes such as fluorescein sodium (FS), indocyanine green (ICG), 5-aminofluorescein-albumin conjugate, hematoporphyrin derivatives including porfimer sodium and 5-aminolevulinic acid (5-ALA), and mono-L-aspartyl chlorin e6 (Npe6). We utilize FS and ICG which leak from the tumor vessels due to the breakdown of the blood-brain barrier. The other dyes are selectively incorporated into the brain tumor cells. 5-ALA, an endogenous substance, is the most commonly used dye because it can be orally administered and is relatively safe. While 5-ALA itself does not produce fluorescence, it is metabolized in the cells to protoporphyrin IX producing red fluorescence.Dyes incorporated into the tumor cells are also used for photodynamic therapy (PDT). At present, however, Npe6 is the only dye approved for PDT against brain tumors in Japan.
