Biological effects and inter-individual variability in peripheral blood lymphocytes of healthy donors exposed to 60 MeV proton radiotherapeutic beam

• Published in: International journal of radiation biology Vol. 94; no. 12; pp. 1085 - 1094
• Main Authors: Panek, Agnieszka, Miszczyk, Justyna, Swakoń, Jan
• Format: Journal Article
• Language: English
• Published: England Taylor & Francis 02.12.2018
• Subjects: Adult; DNA Damage; DNA damage response/repair; DNA Repair; Dose-Response Relationship, Radiation; Female; Humans; Lymphocytes - radiation effects; Male; Middle Aged; Proton Therapy; Protons; RBE; Relative Biological Effectiveness; X-rays; Protons; RBE; DNA damage response/repair; X-rays
• ISSN: 0955-3002; 1362-3095
• DOI: 10.1080/09553002.2019.1524941

Purpose: The aim of our study was to investigate the amount of initial DNA damage and cellular repair capacity of human peripheral blood lymphocytes exposed to the therapeutic proton beam and compare it to X-rays. Materials and methods: Lymphocytes from 10 healthy donors were irradiated in the Spread Out Bragg Peak of the 60 MeV proton beam or, as a reference, exposed to 250 kV X-rays. DNA damage level was assessed using the alkaline version of the comet assay method. For both sources of radiation, dose-DNA damage response (0-4 Gy) and DNA repair kinetics (0-120 min) were estimated. The observed DNA damage was then used to calculate the relative biological effectiveness (RBE) of the proton beam in comparison to that of X-rays. Results: Dose-response relationships for the DNA damage level showed linear dependence for both proton beam and X-rays (R 2  = 0.995 for protons and R 2  = 0.993 for X-rays). Within the dose range of 1-4 Gy, protons were significantly more effective in inducing DNA damage than were X-rays (p < .05). The average RBE, calculated from the proton and X-ray doses required for the iso-effective, internally standardized tail DNA parameter (sT-DNA) was 1.28 ± 0.57. Similar half-life time of residual damage and repair efficiency of induced DNA damage for both radiation types were observed. In the X-irradiated group, significant inter-individual differences were observed. Conclusions: Proton therapy was more effective at high radiation doses. However, DNA damage repair mechanism after proton irradiation seems to differ from that following X-rays.