Purpose: Radiodynamic therapy (RDT) requires a combination of photosensitizer and high-energy photon beam for tumor treatment. Cerenkov light induced by high-energy photon beams activates the photosensitizer, leading to cellular toxicity by producing extra reactive oxygen species to kill malignant cells. The purpose of this study was to investigate the efficacy and photon energy dependency of RDT combined with 5-aminolevulinic acid (5-ALA) using a mouse model.
Methods: The tumors (N=108) were randomized into six groups: control (untreated), 5-ALA only, 6 and 45MV radiation treatment (RT) only, 6MV RDT, and 45MV RDT, to observe individual and synergistic effects of 5-ALA and radiation treatment. 4Gy in a single fraction was delivered to the tumors using two different energy photons for 6 or 45MV RT only and RDT groups. 5-ALA was injected at 100 mg/kg by tail-vein 4 hours before RT for 5-ALA only and 6/45MV RDT groups. Tumor volumes were measured using a 1.5T MR scanner on the day of treatment (prior to treatment, pre-treatment), 3 days post-, 7 days post-, and 14 days post-treatment.
Results: 45MV RDT resulted in a statistically significant delay in tumor growth by 54.4±11.9%, 50.3±10.1%, and 61.5±12.7% compared to 5-ALA, 45MV RT, and the control group (P<0.001), respectively. Moreover, 35.8-43.4% additional decrease in tumor growth was observed, showing a synergistic effect of 45MV RDT. Also, no significant differences were using 6MV RDT, 5-ALA only, 6/45MV RT only, and control groups.
Conclusion: Radiation treatment using 45MV photon with 5-ALA resulted in a significant tumor growth control compared to the other groups. A significant synergistic effect was also observed. 45MV photon beams showed greater 5-ALA activation, improving treatment effect than 6MV. The preliminary results advocate a further investigation into larger sample sizes and demonstrate an effective cancer treatment modality.
Treatment Techniques, MRI, Tumor Control
TH- Small Animal RT: Development (new technology and techniques)