Room: ePoster Forums
Purpose: RECA is a radiation therapy enhancement technique where Cherenkov light generated during the delivery of photon radiation therapy activates intratumorally injected photo-drug, psoralen. Previous in-vitro studies suggest RECA may improve local tumor control and engender anti-tumor immune effect compared to radiotherapy (RT) alone. Here we present results of a preliminary in-vivo study where tumor control and immune response to re-challenged tumor are studied.
Methods: 20 CD57bl/6 mice were injected with 0.5x10â?¶ E0771 tumor cells in the right flank. Tumor sizes were monitored until average size ~200mmÂ³. The mice were randomly distributed into 4 groups of 5 mice: (1) saline injection only, (2) psoralen injection only, (3) RT only, and (4) RECA (RT + psoralen injection). Mice receiving psoralen received 2mg/kg of 8-methoxypsoralen (8-MOP) in physiological saline. Mice receiving radiation were irradiated to 8Gy x 2 fractions at 15MV, collimated to avoid critical structures yet cover the tumor. To assess long-term anti-tumor effect, any mice with regressed tumors were re-injected with 0.5x10â?¶ E0771 at the opposite flank.
Results: A reduction in mean tumor volume were observed for the group of mice treated with RECA (1340Â±540mm3) compared to RT only (1050Â±380mm3) at 26 days post-treatment, albeit statistically not significant (p=0.24). Kaplan-Meier survival curves suggest RECA improves survival compared to saline only control (p=0.03), but not compared to RT only (p = 0.44). No mice survived the tumor, except one mouse out of the five treated with RECA. Re-injection of E0771 tumor cells to this surviving mouse did not result in tumor growth after 90 days, suggesting RECA stimulated a long-term anti-tumor effect.
Conclusion: We report preliminary results of an in-vivo study suggesting RECA may stimulate long-term anti-cancer immunity. However, no statistically significant reduction in tumor size was observed for RECA versus RT. Further studies are required to confirm the observed effect.
Funding Support, Disclosures, and Conflict of Interest: This study was partially funded by Immunolight, LLC