TY - JOUR
T1 - The proton RBE and the distal edge effect for acute and late normal tissue damage in vivo
AU - Overgaard, Cathrine Bang
AU - Reaz, Fardous
AU - Ankjærgaard, Christina
AU - Andersen, Claus E
AU - Sitarz, Mateusz
AU - Poulsen, Per
AU - Spejlborg, Harald
AU - Johansen, Jacob G
AU - Overgaard, Jens
AU - Grau, Cai
AU - Bassler, Niels
AU - Sørensen, Brita Singers
PY - 2025/2
Y1 - 2025/2
N2 - Background and purpose: In proton therapy, a relative biological effectiveness (RBE) of 1.1 is used to reach an isoeffective biological response between photon and proton doses. However, the RBE varies with biological endpoints and linear energy transfer (LET), two key parameters in radiotherapy. Few in vivo studies have investigated the increasing RBE with increasing LET. This study aims to test the hypothesis that the RBE varies between endpoints and has a distal edge effect in vivo. Materials and methods: Unanesthetized mice were restrained in jigs where their right hind legs were irradiated with a single dose of protons at the center (LET, all = 5.3 keV/μm) and distal edge (LET, all = 7.6 keV/μm) of a spread-out Bragg peak (SOBP). 6 MV photons were used as reference. The acute damage and skin toxicity were scored daily until day 30, and the late damage was evaluated using a joint contracture assay for one year after treatment. Results: An acute damage RBE of 1.06 ± 0.02(1.02–1.10) and late damage RBE of 1.16 ± 0.08(1.00–1.32) were found, displaying an enhanced RBE for late damage in the center SOBP. The distal edge RBE for acute and late damage was 1.15 ± 0.02(1.10–1.19) and 1.26 ± 0.09(1.07–1.43), showing a similar center-to-distal edge RBE enhancement of 8 % and 9 % for acute and late damage. Conclusion: The findings demonstrate an increased RBE for late damage than acute damage and the distal edge effect is evident with increased RBE at the distal end of the proton SOBP in vivo.
AB - Background and purpose: In proton therapy, a relative biological effectiveness (RBE) of 1.1 is used to reach an isoeffective biological response between photon and proton doses. However, the RBE varies with biological endpoints and linear energy transfer (LET), two key parameters in radiotherapy. Few in vivo studies have investigated the increasing RBE with increasing LET. This study aims to test the hypothesis that the RBE varies between endpoints and has a distal edge effect in vivo. Materials and methods: Unanesthetized mice were restrained in jigs where their right hind legs were irradiated with a single dose of protons at the center (LET, all = 5.3 keV/μm) and distal edge (LET, all = 7.6 keV/μm) of a spread-out Bragg peak (SOBP). 6 MV photons were used as reference. The acute damage and skin toxicity were scored daily until day 30, and the late damage was evaluated using a joint contracture assay for one year after treatment. Results: An acute damage RBE of 1.06 ± 0.02(1.02–1.10) and late damage RBE of 1.16 ± 0.08(1.00–1.32) were found, displaying an enhanced RBE for late damage in the center SOBP. The distal edge RBE for acute and late damage was 1.15 ± 0.02(1.10–1.19) and 1.26 ± 0.09(1.07–1.43), showing a similar center-to-distal edge RBE enhancement of 8 % and 9 % for acute and late damage. Conclusion: The findings demonstrate an increased RBE for late damage than acute damage and the distal edge effect is evident with increased RBE at the distal end of the proton SOBP in vivo.
KW - Acute damage
KW - Late damage
KW - Linear energy transfer (LET)
KW - Proton radiation
KW - Relative biological effectiveness (RBE)
KW - The distal edge effect
UR - http://www.scopus.com/inward/record.url?scp=85212560107&partnerID=8YFLogxK
U2 - 10.1016/j.radonc.2024.110668
DO - 10.1016/j.radonc.2024.110668
M3 - Journal article
C2 - 39675573
SN - 0167-8140
VL - 203
JO - Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology
JF - Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology
M1 - 110668
ER -