The following is a summary of “Dose-Painting Proton Radiotherapy guided by Functional MRI in Non-Enhancing High-Grade Gliomas,” published in the May 2024 issue of Oncology by Zhu et al.

This study aimed to assess the feasibility and evaluate the dosimetric and clinical implications of dose-painting proton radiotherapy (PRT) guided by functional MRI in patients with non-enhancing high-grade gliomas (NE-HGGs).

The retrospective analysis included ten patients with NE-HGGs who underwent 3D arterial spin labeling (3D-ASL) and T2 fluid-attenuated inversion recovery (FLAIR) MRI before radiotherapy. T2 FLAIR hyperintensity defined the planning target volume (PTV), while the high-perfusion volume on 3D-ASL (PTV-ASL) guided the simultaneous integrated boost (SIB) volume. Each patient received pencil beam scanning PRT and photon intensity-modulated radiotherapy (IMRT). Plans included uniform (IMRT60 vs. PRT60) and SIB (IMRT72, 84, 96, 108 vs. PRT72, 84, 96, 108) approaches to compare dosimetric differences. Biological models assessed tumor control probability (TCP) and normal tissue complication probability (NTCP) for target volumes and organs at risk (OARs).

Compared to IMRT, PRT plans at equivalent prescription doses increased D2 and D50 by 1.27–4.12% and 0.64–2.01%, respectively, and reductions in R30 by >32%. OAR doses, including brainstem, chiasma, and normal brain tissue (Br-PTV), optic nerves, eyeballs, lens, cochlea, spinal cord, and hippocampus, decreased by >27–50% (P < 0.05). Maximum necessary doses were 96 GyE for >98% TCP with PRT and 84 Gy for >91% TCP with IMRT. At maximum dose escalation, the average NTCP for Br-PTV was 1.30% and 1.90% for PRT and IMRT, respectively, with NTCP approaching zero for other OARs in all PRT plans.

Functional MRI-guided dose escalation using PRT is feasible and potentially beneficial for patients with NE-HGG. It enhances TCP while minimizing NTCP for OARs. This retrospective analysis supports PRT-based SIB guided by functional MRI as a promising strategy for optimizing treatment outcomes in NE-HGGs.

Source: sciencedirect.com/science/article/abs/pii/S0936655524001870