Photosensitizer and Radio-Dynamic Therapy (RDT)

Photosensitizers have been widely used for diagnosis and therapy for malignant tumors in clinical setting. Porphyrin compounds have been known as not only a photosensitizer but also radiosensitizer. In clinical neurosurgery, 5-aminolevulinic acid (ALA) is available for intraoperative fluorescence marker for malignant gliomas. Recently, combination therapy using 5ALA and ionizing irradiation for malignant tumors have been investigated. 5-ALA can highly accumulate protoporphyrin IX (PpIX) in mitochondria of tumor cells via the heme biosynthesis. PpIX can induce oxidative stress on mitochondria of tumor cells under the ionizing irradiation exposure. In this review, we discuss radiotherapy using 5-ALA, so called radio-dynamic therapy, for malignant tumors.