Radio-Dynamic Therapy (RDT) Which Combines Cerenkov-Induced PDT And RT

Abstract

Photodynamic therapy (PDT) uses light-activated drugs to treat diseases ranging from cancer to antibiotic-resistant infections. The penetration depth of light has limited clinical applications for PDT. This work investigates the substitute of light in PDT using Cerenkov light induced from 45MV photon from an LA45 therapy accelerator. Compare with the conventional Linacs in radiotherapy, the LA45 accelerator produces higher energy x-ray and leads to emit significant Cerenkov light. So it could be used to replace laser light in PDT and activate effectively photosensitizer to produce singlet oxygen for killing tumor cells. In order to enhance more singlet oxygen production we added a patent coenzyme in the photosensitizers for catalytic action. The 45MV x-ray from LA45 accelerator is delivered to tumor target in 3DCRT, 3-6Gy/f, 1f/w, 6∼4w, as like in external x-ray beam radiotherapy (RT) with conventional Linacs. This therapy method, which combines Cerenkov-induced PDT and RT in one modality, is called as Radio-Dynamic Therapy (RDT).But its main effect is from PDT and RT would add synergistically to PDT. Our Monte Carlo results showed that the Cerenkov light intensity induced from 45MV x ray from an LA45 accelerator is 5-6 times as many as 6MV x-ray from conventional Linacs. Furthermore, the patented catalyst coenzyme enhanced the excitation efficiency to photosensitizers by 3 times. Homogeneous internal excitation efficiency for Cherenkov light in 3DCRT delivery mode is almost 20 times of exponential external of laser irradiation in normal PDT. Accoding to resonance absorption theory of Soret Band, Cerenkov radiation induced by 45MV x-rays can be more effective in activating PpIX to produce singlet oxygen than 630nm laser light in conventional PDT. In clinical trials, the new RDT technique also showed favorable outcomes for specific cancers of early and late stages. Our results indicated that the excitation process and efficiency of the Cerenkov light to photosensitizers from 45MV photons are not only similar as the light in conventional PDT but also overcome the penetration depth limit of light in normal PDT. Comparing the advantages of RDT with a conventional PDT, the RDT is a combinational therapy modality and may be developed into a potential treatment modality for a wider range of cancers stages as well as for other diseases.