Glioblastoma is a high-grade cerebral tumor with local recurrence and poor outcome. Photodynamic
therapy (PDT) is a local treatment based on the light activation of a photosensitizer (PS) in the
presence of oxygen to form cytotoxic species. Fractionation of light delivery may enhance treatment
efficiency by restoring tissue oxygenation.
To evaluate the efficiency of light fractionation using MRI imaging, including diffusion and perfusion,
compared to histological data.
Materials and Methods
Thirty-nine “Nude” rats were grafted with human U87 cells into the right putamen. After PS precursor
intake (5-ALA), an optic fiber was introduced into the tumor. The rats were randomized in three
groups: without illumination, with monofractionated illumination and the third one with multifractionated
light. Treatment effects were assessed with early MRI including diffusion and perfusion sequences.
The animals were eventually sacrificed to perform brain histology.
On MRI, we observed elevated diffusion values in the center of the tumor among treated animals,
especially in multifractionated group. Perfusion decreased around the treatment site, all the more in
the multifractionated group. Histology confirmed our MRI findings, with a more extensive necrosis and
associated with a rarified angiogenic network in the treatment area, after multifractionated PDT.
However, we observed more surrounding edema and neovascularization in the peripheral ring after
Fractionated interstitial PDT induced specific tumoral lesions. The multifractionated scheme was more
efficient, inducing increased tumoral necrosis, but it also caused significant peripheral edema and
neovascularization. Diffusion and perfusion MRI imaging were able to predict the histological lesions.