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Reduced diffusion in white matter after radiotherapy with photons and protons
L Dünger1, A Seidlitz2, C Jentsch2
1ABX-CRO Advanced Pharmaceutical Services Forschungsgesellschaft mbH, Dresden, Germany; OncoRay - National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany.
Radiation therapy for glioblastoma can affect brain white matter. Diffusion imaging shows reduced diffusivity after proton or photon therapy, with protons causing less impact on white matter mean diffusivity (MD).
Area of Science:
- Neuroimaging
- Radiation Oncology
- Medical Physics
Background:
- Adjuvant radio(chemo)therapy is standard for glioblastoma.
- Irradiation of surrounding brain tissue can cause side-effects.
- Diffusion imaging detects early white matter changes post-radiation.
Purpose of the Study:
- Assess white matter mean diffusivity (MD) changes after radio(chemo)therapy.
- Compare MD changes between proton and photon irradiation.
- Investigate dose and time dependency of MD changes.
Main Methods:
- 70 glioblastoma patients (20 proton, 50 photon) underwent therapy.
- MRI follow-ups evaluated up to 33 months post-therapy.
- Relative white matter MD changes calculated in dose regions.
Main Results:
- Significant MD decrease (p < 0.05) in WM regions receiving >20 Gy.
- MD reduction increased with dose and time (max -7.9% at 24 months, ≥50 Gy).
- Photon therapy showed significant whole brain MD reduction; proton therapy did not.
Conclusions:
- Irradiation causes measurable, progressive MD reduction in white matter.
- Proton therapy likely reduces MD changes due to lower surrounding tissue dose.
- Further studies needed to correlate MD changes with side-effects.
