Hypofractionated radiotherapy (RT) combined with dihydroartemisinin (DHA): No synergistic effect observed in a preliminary animal study.

Purpose: Colorectal cancer (CRC) is one of the leading causes of cancer-related death worldwide. Dihydroartemisinin (DHA) is an anti-malaria agent and recent evidence indicates a broad anti-cancer activity. Radiotherapy (RT) is the cornerstone of cancer treatment and often has synergistic effects when combined with chemotherapy or targeted therapy. We aim to investigate whether synergistic effect exists for RT combined with DHA in a preliminary animal study of CRC treatment. Methods: Twenty-four BALB/c nude mice were subcutaneously injected with 5.0 × 10 Results: The tumor weight was 2.4±0.8g, 2.5±0.6g, 0.4±0.2g, and 0.4±0.1g for the control, DHA, RT, and DHA+RT groups, respectively. Significant difference was observed between the control and RT groups, and between the control and DHA+RT groups (p<0.05). However, there was almost no difference between the RT alone and DHA+RT groups. The longitudinal change in tumor volume showed tumor progression inhibition in the RT and DHA+RT groups, but not so obvious in the DHA group, which was consistent with histological assay. Conclusion: Similar treatment efficacy is observed in the RT alone and concurrent DHA+RT group. No significant difference in tumor volume or weight or tumor progression inhibition is observed between the RT alone and concurrent DHA+RT groups, demonstrating that DHA might not provide synergistic effect with RT for the proposed hypofractionated radiation dose regimen.