Dose rateEffect of high dose per pulse flattening filter-free beams on cancer cell survival
Section snippets
Cell culture
The human glioblastoma cell lines T98G, expressing mutated p53, and U87-MG, expressing functional p53, were purchased from the American Type Culture Collection (ATCC). The cells were maintained in monolayer culture in Dulbecco’s Modified Eagle Medium (DMEM) supplemented with 10% FBS, 1% l-Glutamine and 1% Penicillin/Streptomycin. All cells were grown in a humidified atmosphere of 5% CO2 at 37 °C.
Irradiation
Using the TrueBeam STx linear accelerator (Varian Medical Systems, Palo Alto, CA, USA) a pulsed
Increased treatment time increases tumour cell survival
For our study we used flattened as well as FFF beams generated by the TrueBeam STx linear accelerator. Since these two beams differ in their beam profile, we first performed experiments to verify the accuracy of dose application to our in vitro model system as well as the standard deviations within treatments. Two established glioblastoma cell lines, T98G and U87-MG, were irradiated with either 5 or 10 Gy at 10 MV using different dose rates: 20, 400, or 2400 cGy/min. Due to technical limitations
Discussion
The results presented here show that clonogenic survival is statistically reduced if the total dose is delivered with a higher dose per pulse. Indeed, cells irradiated using either the X10 or X10FFF beam show a difference in clonogenic survival which can be explained by the higher dose per pulse delivered by the X10FFF.
Radiation-induced double-strand breaks (DSB) are the most harmful lesions that arise after irradiation because of their impact on genome stability and cell survival [17]. The
Conflict of interest statement
The authors indicated no potential conflicts of interest.
Acknowledgements
We thank Jack Fowler for helpful suggestions and insightful comments, and Michelle Brown for scientific editing. This work was supported by the Department of Radiation Oncology, University Hospital of Zurich, by a research grant from Varian Medical Systems, Inc. (Palo Alto, California), and the foundation Hartmann Mueller (K.Z.).
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