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Whole brain radiotherapy with hippocampal sparing using Varian HyperArc
Cameron J Sprowls1, Amish P Shah1, Patrick Kelly1
1Department of Radiation Oncology, Orlando Health Cancer Institute, Orlando, FL, USA.
Summary
Varian HyperArc improves whole brain radiotherapy (WBRT) with hippocampal sparing, meeting RTOG 0933 criteria. It offers better organ sparing and reduced high-dose volumes compared to VMAT, though planning and delivery take longer.
Area of Science:
- Radiation Oncology
- Medical Physics
- Radiotherapy Planning
Background:
- Whole brain radiotherapy (WBRT) is a common treatment for intracranial lesions.
- Hippocampal sparing is crucial to mitigate cognitive side effects.
- The Radiation Therapy Oncology Group (RTOG) 0933 protocol established dosimetric criteria for hippocampal sparing in WBRT.
Purpose of the Study:
- To evaluate Varian HyperArc as a radiotherapy planning and treatment solution for WBRT with hippocampal sparing.
- To compare HyperArc's dosimetric performance against a 2-arc coplanar VMAT technique using RTOG 0933 criteria.
Main Methods:
- Retrospective planning of WBRT with hippocampal sparing for ten patients using Varian HyperArc and coplanar VMAT.
- Delineation of whole brain and hippocampus on fused MRI/CT datasets.
- Evaluation of dosimetric parameters including PTV dose coverage (V105%), maximum PTV dose, and minimum hippocampal dose.
- Assessment of planning time, delivery time, and delivery quality assurance (QA).
Main Results:
- All HyperArc and VMAT plans met RTOG 0933 dosimetric criteria.
- HyperArc significantly reduced the volume of 105% prescription dose (V105%) to the PTV (6 ± 7%) and the maximum PTV dose (1.3 ± 0.3 Gy).
- HyperArc demonstrated significantly improved organ at risk (OAR) sparing, with a decreased minimum hippocampal dose (0.3 ± 0.3 Gy).
- Coplanar VMAT required shorter planning (2.4 min) and delivery times (1.5 min) compared to HyperArc.
- No significant difference was observed in delivery QA results between the two techniques.
Conclusions:
- Varian HyperArc is a viable solution for WBRT with hippocampal sparing, meeting RTOG 0933 dosimetric standards.
- HyperArc offers superior OAR sparing and reduced high-dose volumes to the planning target volume compared to coplanar VMAT.
- While coplanar VMAT is faster in planning and delivery, HyperArc's dosimetric advantages support its use for improved treatment quality.
