Hippocampal-sparing whole-brain radiotherapy under coplanar or noncoplanar VMAT

Area of Science:

• Radiation Oncology
• Medical Physics

Background:

• Whole-brain radiotherapy (WBRT) is effective for brain metastases but can damage the hippocampus.
• Volumetric modulated arc therapy (VMAT) offers precise radiation delivery, sparing organs-at-risk (OARs).
• Hippocampal-sparing WBRT (HS-WBRT) aims to mitigate radiation-induced cognitive decline.

Purpose of the Study:

• To compare coplanar VMAT (C-VMAT) and noncoplanar VMAT (NC-VMAT) treatment plans for HS-WBRT.
• To evaluate plan quality, OAR doses, and overall treatment efficiency.

Main Methods:

• Ten patients underwent HS-WBRT planning using Eclipse A10.
• Three VMAT techniques were generated: C-VMAT, NC-VMAT A (NC-A), and NC-VMAT B (NC-B).
• Plans were assessed based on RTOG 0933 OAR constraints, dose conformity, homogeneity, and maximum doses.

Main Results:

• C-VMAT achieved the lowest OAR doses (hippocampus, brain stem, optic chiasm).
• No significant difference in dose conformity was observed among the techniques.
• NC-A demonstrated superior homogeneity and intermediate OAR sparing, while C-VMAT showed the best overall performance considering plan quality and efficiency.

Conclusions:

• Coplanar VMAT is a suitable technique for HS-WBRT, offering a balance of plan quality and efficiency.
• C-VMAT may reduce patient alignment and total treatment time compared to noncoplanar approaches.
• Further investigation into optimizing VMAT techniques for HS-WBRT is warranted.