Microbeam Irradiation as a Simultaneously Integrated Boost in a Conventional Whole-Brain Radiotherapy Protocol

Area of Science:

• Radiation Oncology
• Pre-clinical Cancer Research

Background:

• Microbeam radiotherapy (MRT) is an experimental technique using high-dose rates and spatial fractionation at the micrometer level.
• Pre-clinical studies suggest MRT has significant therapeutic potential and preserves normal tissue function.

Purpose of the Study:

• To evaluate the efficacy of MRT as a simultaneously integrated boost (SIB) within conventional whole-brain irradiation (WBRT).
• To determine the optimal timing for integrating an MRT SIB in a radiotherapy schedule.

Main Methods:

• A 174 Gy MRT SIB was delivered using 50 µm microbeams spaced 400 µm apart.
• The MRT SIB was administered on either the first or last day of a 5 × 4 Gy WBRT schedule in C57 BL/6J mice and F98 glioma cell cultures.
• Animals were monitored for adverse effects; F98 cell cultures were assessed for tumoricidal effect via colony counts.

Main Results:

• No acute adverse effects were observed in irradiated animals within 3 days post-treatment.
• The tumoricidal effect on F98 cells in vitro was significantly greater when the MRT SIB was delivered on the first day compared to the last day of irradiation.
• Early integration of MRT SIB demonstrated superior efficacy.

Conclusions:

• Microbeam radiotherapy is a viable option for simultaneously integrated boost delivery in conventional radiotherapy.
• Integrating the MRT SIB early in the treatment course maximizes its tumoricidal effect.
• Clinical radiotherapy schedules should consider incorporating the MRT SIB as early as possible for enhanced outcomes.