Enhanced DNA Damages of Human Prostate Cancer Cells Induced by Radiofrequency Capacitive Hyperthermia Pre- and Post X-rays: 6 MV versus 15 MV

OBJECTIVE: This study aimed to determine the effect of 13.56 MHz radiofrequency (RF) capacitive hyperthermia (HT) on radiosensivity of human prostate cancer cells pre and post X-ray radiation treatment (RT). MATERIALS AND METHODS: In this experimental study, the human prostate cancer cell line DU145 was cultured as 300 µm diameter spheroids. We divided the spheroids into group I: control, group II: HT at 43˚C for 30 minutes (HT), group III: 4 Gy irradiation with 6 MV X-ray [RT (6 MV)], group IV: 4 Gy irradiation with 15 MV X-ray [RT (15 MV)], group V: HT+RT (6 MV), group VI: HT+RT (15 MV), group VII: RT (6 MV)+HT, and group VIII: RT (15 MV)+HT. The alkaline comet assay was used to assess DNA damages in terms of tail moment (TM). Thermal enhancement factor (TEF) was obtained for the different treatment combinations. RESULTS: Mean TM increased with increasing photon energy. Group II had significantly greater TM compared to group I. Groups III and IV also had significantly higher TM compared to group I. Significant differences in TM existed between groups V, VII, and III (P<0.05). We observed significant differences in TM between groups VI, VIII, and IV. TEF values demonstrated that enhanced response to radiation was more pronounced in group V compared to the other combined treatments. CONCLUSION: Our results suggest that HT applied before RT leads to higher radiosensivity compared to after RT. HT at 43˚C for 30 minutes added to 6 MV X-ray causes higher enhancement of radiation compared to 15 MV X-ray.