Whole brain radiotherapy with hippocampal avoidance and simultaneously integrated brain metastases boost: a planning...

Area of Science:

• Radiation Oncology
• Medical Physics

Background:

• Whole brain radiotherapy (WBRT) is a standard treatment for brain metastases.
• Hippocampal avoidance during WBRT aims to mitigate neurocognitive side effects, particularly memory decline.
• Simultaneous integrated boost (SIB) can enhance tumor control in brain metastases.

Purpose of the Study:

• To assess the feasibility of using tomotherapy for WBRT with hippocampal avoidance and SIB to brain metastases.
• To evaluate the impact of tomotherapy parameters on dose distribution and treatment planning.

Main Methods:

• Ten patients previously treated with WBRT and radiosurgery underwent repeat planning with tomotherapy.
• Hippocampal dose was limited to <6 Gy, WBRT dose was 32.25 Gy, and SIB doses varied by metastasis size (63 Gy or 70.8 Gy).
• Tomotherapy plans were generated using field widths of 2.5 cm and 1.0 cm for comparison.

Main Results:

• A 1.0-cm field width significantly improved dose distribution and whole brain homogeneity by 32% compared to 2.5-cm.
• Hippocampal mean normalized total dose remained low (<6 Gy(2)) with both field widths.
• Treatment delivery time increased with the narrower field width (10.2 min vs. 21.8 min).

Conclusions:

• Composite tomotherapy plans successfully achieved homogeneous WBRT dose distribution.
• Conformal hippocampal avoidance was feasible, protecting the hippocampus from high radiation doses.
• Radiosurgically equivalent dose distributions to individual brain metastases were delivered simultaneously.