Verification of radiodynamic therapy by medical linear accelerator using a mouse melanoma tumor model

Combined treatment with 5-aminolevulinic acid (5-ALA) and X-rays improves tumor suppression in vivo. This is because the accumulated protoporphyrin IX from 5-ALA enhances the generation of ROS by the X-ray irradiation. In the present study, a high-energy medical linear accelerator was used instead of a non-medical low energy X-ray irradiator, which had been previously used. Tumor-bearing mice implanted with B16-BL6 melanoma cells were treated with fractionated doses of irradiation (in total, 20 or 30 Gy), using two types of X-ray irradiator after 5-ALA administration. Suppression of tumor growth was enhanced with X-ray irradiation in combination with 5-ALA treatment compared with X-ray treatment alone, using both medical and non-medical X-ray irradiators. 5-ALA has been used clinically for photodynamic therapy. Thus, “radiodynamic therapy”, using radiation from medical linacs as a physical driving force, rather than the light used in photodynamic therapy, may have potential clinical applications.