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The Effect of Flattening Filter-Free Beams with Different Single Fraction Doses On the Survival of Prostate Cancer Cell

C Ceylan1*, A Ozturk2 , G Gungor3 , G Duruksu2 , Y Yazir2 , G Aksu2 , O Gundogdu2 , (1) Istanbul Oncology Hospital, Istanbul, TR, (2) Kocaeli University, Kocaeli, TR, (3) Acibadem University, Istanbul, TR,


(Sunday, 7/29/2018) 3:00 PM - 6:00 PM

Room: Exhibit Hall

Purpose: The investigation of radiobiological response differences in cancer cell survival was done using a high dose per pulse flattening filter-free (FFF) beam compared to a standard flattened beam for single fraction dose >10 Gy SRS/SBRT.

Methods: 6 MV and 6 FFF beams were used to compare the radiobiological effect on DU-145 prostate cancer cell of altering dose rate, dose per pulse and reducing treatment time with either 10Gy/1fx or 20 Gy/1fx. The counting of cells was performed with the incubated cells by WST-1 test 4-5 days after irradiation.

Results: The results for DU-145 demonstrate that filtered and FFF 6 MV with same dose rate and treatment time has no effect on cell survival in the DU-145 which were irradiated both 10 and 20 Gy single fraction doses. The average dose-rate of the 6FFF beam was varied by increasing the x-ray pulse repetition rate to irradiated cells with 600 Mu/min and 1400 MU/min. Statically significant differences was observed between cells which were irradiated with 6 MV 600 MU/min and 6 MV FFF 1400 MU/min (p=0.024). Although there was no survival difference between the cells which were irradiated with 6 MV FFF 600 MU/min and 6 MV FFF 1400 MU/min for 10 Gy. The statically significant survival difference was obtained for 20 Gy single fraction. The experiments for CyberKnife irradiation which has 800 MU/min constant dose rate were done for 10 Gy and 20 Gy fraction doses. The survival cell percentages for both 10 Gy and 20 Gy single fraction doses with Cyberknife were obtained higher than FF and FFF which have 600 MU/min dose rate.

Conclusion: Our in vitro study presented here show that higher dose rate and reduced treatment time might become a crucial factor for especially SBRT which has >10 Gy fraction dose.


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