Relative Biological Efficiency Research Articles

Biological Response of Chinese Hamster B14-150 Cells to Sequential Combined Exposure to Protons and 12C Ions.

Proton and ion radiation therapy, when used both as single radiation and in mixed radiation mode, have a number of advantages over the conventional γ-therapy that are determined by physical characteristics of accelerated particles. The paper presents the results of an in vitro study of the effectiveness of sequential exposures of Chinese hamster tumor cells B14-150 to proton (p) and 12C ion beams. We used 4 irradiation schemes differing by the sequence of exposure and the contribution of each radiation to the total dose. Synergism was shown for 12C ions dose contribution of 45% (taking into account the coefficient of relative biological efficiency) and the sequence 12C→p.

Assessing the nutritional equivalency of DL-methionine and L-methionine in broiler chickens: a meta-analytical study

The purpose of this study was to perform a meta-analysis comparing the biological efficiency of DL-methionine and L-methionine (DL-Met and L-Met) in broiler nutrition. This analysis was based on a dataset comprising experiment results published in peer-reviewed papers since 2007. All experiments investigated the response of broilers (aged 0-21 d) to different dietary concentrations of DL- and L-Met, achieved by supplementing crystalline Met. A graphical analysis was conducted on the database using ellipses coverage and nonparametric density techniques. Two methods of linear and nonlinear exponential meta-regression analysis were used to determine relative bioavailability based on average daily gain (ADG) and feed conversion ratio (FCR) responses to dietary Met sources. The analyses of ADG and FCR obtained from both linear and exponential models showed a relative difference between the tested methionine sources. The results showed that both ADG and FCR were improved in L-Met compared to DL-Met supplemented diets. Linear regression analysis revealed that DL-Met was 94.97% (for ADG) and 95.63% (for FCR) as efficacious as L-Met (P < 0.01). In contrast, the analysis of the fitted nonlinear exponential model showed that the biological efficiencies of DL-Met were 91.33% and 76.57% of the values for L-Met for ADG (P=0.01) and FCR (P=0.09), respectively. Based on the meta-analytical results, an equivalence of relative biological efficiency of DL-Met in comparison with L-Met for young broilers could not be confirmed.

Cellular irradiations with laser-driven carbon ions at ultra-high dose rates

Objective. Carbon is an ion species of significant radiobiological interest, particularly in view of its use in cancer radiotherapy, where its large Relative Biological Efficiency is often exploited to overcome radio resistance. A growing interest in highly pulsed carbon delivery has arisen in the context of the development of the FLASH radiotherapy approach, with recent studies carried out at dose rates of 40 Gy s−1. Laser acceleration methods, producing ultrashort ion bursts, can now enable the delivery of Gy-level doses of carbon ions at ultra-high dose rates (UHDRs), exceeding 109 Gy s−1. While studies at such extreme dose rate have been carried out so far using low LET particles such as electrons and protons, the radiobiology of high-LET, UHDR ions has not yet been explored. Here, we report the first application of laser-accelerated carbon ions generated by focussing 1020 W cm−2 intense lasers on 10–25 nm carbon targets, to irradiate radioresistant patient-derived Glioblastoma stem like cells (GSCs). Approach. We exposed GSCs to 1 Gy of 9.5 ± 0.5 MeV/n carbon ions delivered in a single ultra-short (∼400-picosecond) pulse, at a dose rate of 2 × 109 Gy s−1, generated using the ASTRA GEMINI laser of the Central Laser Facility at the Rutherford Appleton Laboratory, Didcot, Oxfordshire, UK. We quantified carbon ion-induced DNA double strand break (DSB) damage using the 53BP1 foci formation assay and used 225 kVp x-rays as a reference radiation. Main Results. Laser-accelerated carbon ions induced complex DNA DSB damage, as seen through persistent 53BP1 foci (11.5 ± 0.4 foci/cell/Gy) at 24 h and significantly larger foci (1.69 ± 0.07 μm2) than x-rays induced ones (0.63 ± 0.02 μm2). The relative foci induction value for laser-driven carbon ions relative to conventional x-rays was 3.2 ± 0.3 at 24 h post-irradiation also confirming the complex nature of the induced damage. Significance. Our study demonstrates the feasibility of radiobiology investigations at unprecedented dose rates using laser-accelerated high-LET carbon ions in clinically relevant models.

Carbon Radiotheraphy For Head and Neck Cancer: Dosimetric Comparison with Photon Plans

Radiation therapy is one of the most widely used treatment methods for tumors. The therapeutic use of carbon ions is more advantageous than other radiotherapy techniquies especially photon-based irradiation due to its physical properties and radiobiological effects, and therefore it has received more attention. One of the most important reasons for that carbon ion beams are more effective than photon beams while minimizing the dose in the normal tissues around the target, it offers an improved dose distribution that leads to sufficient dose concentration in tumors. In addition, the carbon beam reaches its maximum at the end of its range, which increases with depth, and due to this feature, it provides a higher biological efficiency. In radiotherapy studies, Monte Carlo simulation is widely used to determine the dose distributions and to obtain the correct properties of the beams. With MC simulation, it helps to understand the relative biological efficiency as well as the spatial model of energy storages. In this study, a geometry with critical organs (skull, brain, nasopharynx and thyroid) based on a MIRD phantom was modeled with the Monte Carlo simulation tool GATE (vGATE 9.0). In this experiment, the tumor was irradiated with different carbon beam energies and photon beams. The aim is to calculate the energy accumulations in the region and surrounding organs with the MC method, and as a result, to show the dosimetric advantages of carbon radiotherapy over photon radiotherapy.

Calculation of the Biological Efficiency of the Proton Component from 14.8 MeV Neutron Irradiation in Computational Biology with Help of Video Cards.

Fast neutron therapy, which previously has demonstrated effective results, but along with a large number of complications, can again be considered a promising treatment method in the treatment of cancer. One of the ways of analyzing the relative biological efficiency and accurate biological dose of fast neutrons in body tissues is to improve the algorithms of computational biology and mathematical modeling. A high-performance computing code was written which allows to estimate in real-time mode the biological dose of the proton component from the action of neutron radiation with an energy of 14.8 MeV. A comparative analysis of the computing performance on various video cards was also performed.

Cultivation of Different Oyster Mushroom (Pleurotus species) on Coffee Waste and Determination of Their Relative Biological Efficiency and Pectinase Enzyme Production, Ethiopia.

Cultivation of specialty mushrooms on lignocellulosic wastes represents one of the most economic and cost-effective organic recycling processes. Solid-state cultivation (SSC) was carried out to evaluate the feasibility of using coffee waste (husk and parchment) as substrate for cultivation of oyster mushroom (Pleurotus species). The periods for spawn running, pinhead and fruit body formation, number of flushes, yield, and biological efficiency of the four Pleurotus species (P. citrinopileatus, P. eryngii, P. ostreatus, and P. sapidus) grown on coffee husk and parchment were studied. The results revealed that the time for the first appearance of pinhead was shortest for P. ostreatus (20–21) days followed by P. sapidus (22–23) days on coffee husks, while P. eryngii and P. citrinopileatus required 26–27 days and 23–24 days, respectively, on the some substrate. All the four Pleurotus species recorded at least four flushes and three flushes on coffee husk and parchment, respectively; flush 1 gave the highest yield while flush 3 and 4 gave the lowest yield. The biological efficiency (B.E.) for P. citrinopileatus, P. eryngii, P. ostreatus and P. sapidus obtained from fresh coffee husk was 26.54, 40.94, 60.33, and 55.72, respectively. Significant differences (P < 0.05) in yield and % B.E. of the four mushrooms species were recorded. The results also showed that the B.E. (61.92%) of P. ostreatus grown on composted coffee husk was insignificantly higher (P < 0.05) than that grown on noncomposted coffee husk (60.33). The yields of P. sapidus obtained from the two substrates were almost comparable with that of P. ostreatus. There was a significant difference at (P < 0.05) observed between noncomposted and composted coffee husk and coffee parchment as well as between coffee husk and coffee parchment on yield and biological efficiency (B.E.). Composted coffee waste is more efficient than noncomposted one. Pectinase enzymes productions by these mushrooms were also studied. They are known to produce extracellular enzymes, particularly pectinase, which contribute to the biochemical decomposition of pectin-rich lignocellulosic wastes biomass. Accordingly, P. sapidus showed more pectolytic activities followed by P. ostreatus. But the pectolytic activity showed by P. eryngii and P. citrinopileatus was relatively lower. The implications of this study are the feasibility of using composted coffee husks and coffee parchment with the supplementary substrate to cultivate very protein-rich mushrooms for food in solid-state cultivation (SSC) while at the same time promoting environmental sustainability.

In vitro modified microdosimetric kinetic model–based predictions for B14-150 cells survival in 450 MeV/u carbon ion beam with aluminum ridge filter for biologically optimized spread-out Bragg peak

The relative biological efficiency of particle irradiation could be predicted with a wide variety of radiobiological models for various end-points. We validate the forecast of modified Microdosimetric Kinetic Model in vitro using combined data of reference Co-60 radiation and carbon ion plateau data for specific cell line to optimize the survival function in spread-out Bragg Peak obtained with an especially designed ridge filter. We used Geant4 Monte-Carlo software to simulate the fragment contribution along Bragg curve inside water phantom, open-source toolkit Survival to predict the expected linear-quadratic model parameters for each fragment, and in-house software to form the total survival curve in spread-out Bragg Peak. The irradiation was performed at U-70 synchrotron with an especially designed Aluminum ridge filter under the control of PTW and in-house ionization chambers. The cell clonogenic assay was conducted with the B14–150 cell line. The data analysis was accomplished using scipy and CERN ROOT. The clonogenic assay represents the survival in spread-out Bragg Peak at different points and qualitatively follows the modeled survival curve very well. The quantitative difference is within 3σ, and the deviation might be explained by the uncertainties of physical modeling using Monte-Carlo methods. Overall, the obtained results are promising for further usage in radiobiological studies or carbon ion radiotherapy. Shaping the survival curve in the region of interest (i.e., spread-out Bragg Peak) is a comprehensive task that requires high-performance computing approaches. Nevertheless, the method’s potential application is related to the development of next-generation treatment planning systems for ion beams. This can open a wide range of improvements in patient treatment outcome, provide new optimized fractionation regimes or optimized dose delivery schemes, and serve as an entrance point to the translational science approach.

Response of murine neural stem/progenitor cells to gamma-neutron radiation

Purpose In recent years, a growing number of studies have focused on the mechanisms of action of densely ionizing radiation. This is associated with the development of radiation therapy of tumors using accelerated ions. The use of densely ionizing radiation appears to be the most promising method, optimal for treating patients with severe radioresistant forms, such as widespread head and neck tumors, recurrent and metastatic tumors, and some forms of brain tumors. The goal of our study was to investigate the effects of gamma-neutron radiation on mouse neural stem/progenitor cells (NSCs/NPCs). Methods NSCs/NPCs were isolated from neonatal mouse brains. Cells were irradiated in a collimated beam of neutrons and gamma rays of the IR-8 nuclear reactor. At 5 and 7 days after irradiation, cells and neurospheres were counted to assess survival. The number of DNA double-strand breaks and their repair efficiency were determined by immunocytochemical γH2AX staining followed by counting the number of γH2AX foci using a fluorescent microscope. Results We observed a dose-dependent decrease in the survival of NSCs/NPCs after irradiation at doses above 100 mGy and stimulation of the proliferation of these cells at doses of 25 and 50 mGy. In terms of a decrease in cell survival, the effect of gamma-neutron irradiation significantly exceeded the effect of gamma irradiation: the maximum value of the relative biological efficiency for gamma-neutron irradiation comprised 9.7. Gamma-neutron irradiation led to the formation of double-strand DNA breaks detected by the formation of foci of histone γH2AX in the cell nuclei. The γH2AX foci formed after gamma-neutron irradiation of NSCs/NPCs at doses of 100–500 mGy were characterized by a larger size in comparison with foci induced by gamma irradiation and gamma-neutron irradiation at a dose of 50 mGy. The repair of double-strand DNA breaks induced by γ,n-irradiation was slow; the repair rate depended on the radiation dose. Conclusions The data obtained indicate high sensitivity of proliferating NSCs/NPCs to gamma-neutron radiation. High RBE of gamma-neutron radiation requires special measures to protect the neurogenic regions of the brain when using this type of radiation in radiation therapy.

Assessment of the Relative Biological Efficiency of Pencil Beam Scanning of Protons in Mice in Vivo.

The effect of proton pencil beam scanning in the dose range of 4.5-15 Gy on the radiosensitivity of mice under irradiation in two regions of the Bragg curve was studied according to the criteria of 30-day survival, dynamics of death, and average lifespan of mice. The relative biological effectiveness (RBE) value of protons relative to X-ray radiation before and at the Bragg peak determined by the LD50/30 index was 0.86 and 0.94, respectively, and by the criterion of 30-day survival at a dose of 6.5 Gy it was 0.83 and 0.84, respectively. With similar RBE values for protons in different regions of the Bragg curve, significant differences in the dynamics of the course of radiation sickness were revealed, which indicates different damage to critical systems and organs of animals and the induction of compensatory mechanisms involved in the formation of stress responses at the organismal level.

Nuclear reactions for protontherapy intensification

This paper presents some experimental results about the 7Li, 11B and 19F (p, α) nuclear reactions developed using proton beams at energy below 3 MeV in order to be applied to protontherapy. The energy released by proton beams during radiotherapy acts mainly at the end of the proton path in the biological medium, where it increases at high density inside the tumor. At this depth, it is possible to inject in the tumor compounds containing Li, B and F to generate energetic alpha particles from nuclear reactions. At the proton Bragg peak position it is possible to produce 1–8 MeV alpha particles, which enhance the energy density deposited in the tumor increasing the probability to damage the cells. Thanks to the higher relative biological efficiency of the alpha particles with respect to protons, it is expected that the alpha synergic particles defeat the tumor at lower doses.

Real-time in-vivo dosimetry for DaRT

Diffusing alpha-emitters radiation therapy (DaRT) is a revolutionary brachytherapy technique used to treat solid tumours. Implant seeds are coated with 224Ra which, along its shortlived daughter atoms, emits alpha particles of high linear energy transfer (LET) and of high relative biological efficiency (RBE), creating a tumour-killing dose distribution a few mm wide. Those alpha particles are of energy between 5.67 and 8.78 MeV. DaRT is under investigation in clinical trials, but there currently is no obvious solution for dosimetry aimed at quality assurance of treatment. This study introduces alpha-RAD, a dosimeter based on a metal-oxide-semiconductor (MOS) sensor technology. Alpha-RAD was characterized with 241Am, which emits alpha particles of energy 5.49 MeV. The results showed that alpha-RAD had good linearity with dose, with the signal increasing linearly in the range from 0 to 6.84 Gy. Also, an external bias in the range between 15 and 60 V, applied on the gate of alpha-RAD during irradiation, would optimize sensitivity to alpha particles of energies typical of DaRT. Alpha-RAD, owing to its compactness, can fit into a brachytherapy needle, to be placed next to 224Ra seed implants in the tumour, for real-time in vivo dosimetry.

Image-based Approach for Absorbed Dose Estimation of 64Cu/225Ac-DOTA-trastuzumab using Monte Carlo Simulation

Image-based absorbed dose calculation studies have been performed to evaluate the characteristics of theranostic radiopharmaceuticals. The aim of this study was to evaluate the 64Cu and 225Ac-DOTA-trastuzumab absorbed dose in mice using image-based Monte Carlo simulation. 64Cu-DOTA-trastuzumab PET image was acquired at 3 time point at 3, 24, and 48 hour after radiopharmaceuticals injection in mice. Time-integrated activity coefficient in source organs called residence time was calculate in region of interest (ROI) delineable organs. Image-based source organ 64Cu/225Ac S-value were calculate using Geant 4 Monte Carlo simulation. Absorbed dose for 225Ac-DOTA-trastuzumab was calculated by 64Cu-DOTA-trastuzumab residence time and Monte Carlo simulated 225Ac dose map. The relative biological efficiency (RBE) of the alpha particles emitted from 225Ac, was estimated to be 5 (RBE = 5). 225Ac-DOTA-trastuzumab absorbed dose was considered all decay step of 225Ac radioisotopes (221Fr, 217At, 213Bi, 213Po, 209Tl and 209Pb) and summed up after applying weighting factors in the two possible pathways, 2% for 209Tl and 98% for 213Po. Residence time of 64Cu-DOTA-trastuzumav in liver was 1.80 MBq-h/MBq that is high uptake region in normal subject. Liver absorbed dose of 64Cu- and 225Ac DOTAtrastuzumab were 2.73E-02 mGy/MBq, 6.37E+00 SvRBE5/MBq. 64Cu-DOTA-trastuzumab absorbed dose in lung, kidney, and spleen were 2.97E-03, 3.86E-04, 3.62E-05 mGy/MBq, respectively. 225Ac-DOTA-trastuzumab absorbed does in lung, kidney, and spleen were 3.10E01, 9.18E-02, 9.12E-03 SvRBE5/MBq, respectively. 225Ac-DOTA-trastuzumab absorbed dose was 2.34E+02 fold higher than 64Cu-DOTA-trastuzumab. We performed the 64Cu-DOTA-trastuzumab PET imaging and estimated the image-based internal absorbed dose of 225Ac-DOTA-trastuzumab. This result may help to strategy of treatment for HER2-positive cancer patients using targeted alpha therapy of 225Ac radioisotope.

Relative biological efficiency of ionizing radiation that is used in radiation therapy of cancer patients

Relative biological efficiency of ionizing radiation that is used in radiation therapy of cancer patients

Assessment of the Biological Efficiency of 450 MeV/Nucleon Accelerated Carbon Ions in the U-70 Accelerator According to the Criterion of Mouse Survival

Abstract—The coefficients of the relative biological efficiency of a carbon ion beam with an energy of 450 MeV/nucleon upon the irradiation of mice at a dose of 6.5 Gy in different parts of the Bragg curve have been determined by the 30-day survival test, the dynamics of death, and the average life expectancy of mice in comparison with exposure to X-ray radiation. The integral value ​​of the coefficients of the relative biological efficiency of carbon ions upon irradiation before the Bragg peak is 0.8, in the spread-out Bragg peak it is 1.5, and after the Bragg peak, it is 0.7. The value of the relative biological efficiency in the modified Bragg peak, as calculated by the ratio of doses that lead to the death of 50% of the animals, was 2.9. Changes of the width of the modified Bragg peak did not affect the death rate of the animals.

Исследование потока тормозных фотонов и нейтронов при работе медицинского ускорителя электронов

Purpose: To estimate the contribution of the secondary neutron flux to the total radiation flux during the operation of Trilogy linear medical accelerator and Varian’s Clinac 2100 accelerator for assessment of impact on the health of patients and medical personnel. &#x0D; High-energy linear accelerators operating at energies higher than 8 MeV generate neutron fluxes when interacting with accelerator elements and with structural materials of the room for treating patients. Neutrons can form at the accelerator head (target, collimators, smoothing filter, etc.), the procedure room, and directly in the patient’s body.&#x0D; Because of the high radiobiological hazard of neutron radiation, its contribution to the total beam flux, even at a level of few percent, substantially increases the dose received by the patient.&#x0D; Material and methods: Secondary neutron fluxes were investigated during the process of the linear medical accelerators Trilogy and Clinac 2100 of Varian operation by the photoactivation method using (γ, n) and (n, γ) reactions on the detection target of natural 181Ta. In addition, measurements of neutron spectra were carried out directly in the room during the operation of a medical accelerator using a spectrometer-dosimeter SDMF-1608.&#x0D; Results: It was determined that the neutron flux on the tantalum target is 16 % of the gamma-ray flux on the same target when the accelerator is operated with a 18 MeV bremsstrahlung energy and 5 % when the accelerator is operated with a 20 MeV excluding thermal neutrons.&#x0D; Conclusion: Finally, it may be noted that, taking into account the coefficient of relative biological efficiency (RBE) of neutron radiation for neutrons with energies of 0.1–200 keV equal to 10 compared with the RBE coefficient for gamma quanta (equal to 1), even preliminary analysis demonstrates significant underestimation of the contribution of neutrons dose to the total dose received by the patient in radiation therapy using bremsstrahlung of 18 and 20 MeV.

Comparative Analysis of the Formation of γH2AX Foci in Human Mesenchymal Stem Cells Exposed to 3H-Thymidine, Tritium Oxide, and X-Rays Irradiation.

We performed a comparative study of the formation of γН2АХ foci (a marker of DNA doublestrand breaks) in human bone marrow mesenchymal stem cells after 24-h incubation with 3Н-thimidin and tritium oxide with low specific activities (50-800 MBq/liter). The dependence of the number of γH2AX foci on specific activity of 3H-thymidine was described by a linear equation y=2.21+43.45x (R2=0.96), where y is the number of γH2AX foci per nucleus and x is specific activity in 1000 MBq/liter. For tritium oxide, the relationship was described by a linear equation y=2.52+6.70x (R2=0.97). Thus, the yield of DNA double-strand breaks after exposure to 3H-thymidine was 6.5-fold higher than after exposure to tritium oxide. Comparison of the effects of tritium oxide and X-ray radiation on the yield of DNA double-strand breaks showed that the relative biological efficiency of tritium oxide in a dose range of 3.78-60.26 mGy was 1.6-fold higher than that of X-ray radiation. Improvement of the methods of analysis of DNA double-strand breaks repair foci is highly promising in the context of creation of highly sensitive biodosimetry technologies for tritium compounds in humans.

ScCVD Diamond Membrane based Microdosimeter for Hadron Therapy

Hadron therapy is an innovative mode of radiotherapy (RT) for cancer treatment which enables tumor cells to be more effectively destroyed than conventional RT using photons. The precise knowledge of the lineal energy of particles is used in the field of microdosimetry (MKM model) as a fundamental parameter in the prediction of the relative biological efficiency (RBE) of clinical beams. Based on single‐crystal CVD (scCVD) super‐thin diamond membranes obtained using deep Ar/O2 plasma etching, prototypes of solid‐state microdosimeters for lineal energy measurements are produced at the Diamond Sensors Laboratory of CEA‐LIST. The response of a diamond membrane microdosimeter to single projectiles is investigated in ion microbeams. The microdosimeter is irradiated using a raster scanning method and the charge transport properties of the device are determined with sub‐micron precision by measuring the charge collection efficiency (CCE), the μSVs 3D spatial definition and the pulse‐height spectra. A prototype of this novel microdosimeter is then tested in a 100 MeV therapeutic proton beam at the Institute Curie − Proton Therapy Centre in Orsay. All results effectively demonstrate the great potential for this device to be used for studies of the RBE in clinical applications.

BIOLOGICAL EFFICIENCY OF THE PROTON SCANNING BEAM OF THE THERAPEUTIC COMPLEX "PROMETHEUS" OF THE A.F. TSYB MEDICAL RADIOLOGICAL RESEARCH CENTER IN STUDIES ON CELL CULTURE OF MURINE MELANOMA B-16

The basis for the use of protons for radiation therapy tasks is a fixed conventional value of their relative biological efficiency equal to 1,1. Numerous studies have showed that RBE of proton radiation is not a constant value and depends on a number of factors. The purpose of this study was to determine RBE of a thin scanning proton beam at the center of the distributed Bragg peak in experiments on the culture of murine B-16 melanoma cells. The cell suspension was irradiated in an aqueous phantom by a horizontal proton beam from three directions (0,90 and 180°) in doses from 2 to 8 Gy. Modulation of the energy of proton radiation was 47,5÷92,0 MeV. RBE protons were determined from the clonogenic activity of the cells compared with 60Co gamma quanta. A linear-quadratic model was used to construct the dose dependencies. Obtained RBE values of proton radiation (LET 3÷8 keV/μm) differed in the big party from the generally accepted value and was at the level of 10% survival rate of 1.5. The results obtained generally coincided with data of foreign authors performed on different facilities.

Development of binary technologies of radiotherapy of malignant neoplasms: condition and problems

The review is devoted to the problems of the development of binary technologies of radiation therapy - neutron and photon-capture therapy of malignant neoplasms. These technologies are based on the principle of “biological” targeting: irradiation of a tumor with pre-delivered special preparations increasing energy release and the relative biological efficiency of primary radiation. The basis of methods, characteristics of sources of external irradiation and used preparations, and stages of development of technologies are described. The development and implementation of binary technologies attract a great number of researchers but are restrained by the shortage of operating sources of epithermal neutrons (reactors, neutron generators based on accelerators) and the lack of accurate radiation dosimetry planning systems that takes into account the dynamics and accumulation of drugs in tumors.

Influence of Dose Rate on the Cellular Response to Low- and High-LET Radiations.

Nowadays, head and neck squamous cell carcinoma (HNSCC) treatment failure is mostly explained by locoregional progression or intrinsic radioresistance. Radiotherapy (RT) has recently evolved with the emergence of heavy ion radiations or new fractionation schemes of photon therapy, which modify the dose rate of treatment delivery. The aim of the present study was then to evaluate the in vitro influence of a dose rate variation during conventional RT or carbon ion hadrontherapy treatment in order to improve the therapeutic care of patient. In this regard, two HNSCC cell lines were irradiated with photons or 72 MeV/n carbon ions at a dose rate of 0.5, 2, or 10 Gy/min. For both radiosensitive and radioresistant cells, the change in dose rate significantly affected cell survival in response to photon exposure. This variation of radiosensitivity was associated with the number of initial and residual DNA double-strand breaks (DSBs). By contrast, the dose rate change did not affect neither cell survival nor the residual DNA DSBs after carbon ion irradiation. As a result, the relative biological efficiency at 10% survival increased when the dose rate decreased. In conclusion, in the RT treatment of HNSCC, it is advised to remain very careful when modifying the classical schemes toward altered fractionation. At the opposite, as the dose rate does not seem to have any effects after carbon ion exposure, there is less need to adapt hadrontherapy treatment planning during active system irradiation.