SU-E-T-557: A Planning Strategy of Volumetric Modulated Arc Therapy with Simultaneous Integrated Boost for...

Area of Science:

• Radiation Oncology
• Medical Physics
• Neurosurgery

Background:

• Intracranial stereotactic radiotherapy requires precise dose delivery to target volumes while sparing surrounding healthy brain tissue.
• Volumetric modulated arc therapy (VMAT) offers advanced dose shaping capabilities compared to traditional techniques.
• Simultaneous integrated boost (SIB) allows for dose escalation within a target volume during radiotherapy treatment.

Purpose of the Study:

• To evaluate the dosimetric impact of dose escalation using SIB-VMAT for intracranial stereotactic radiotherapy.
• To compare the conformity and normal tissue sparing of SIB-VMAT with dynamic conformal arc therapy (DCA) and standard VMAT.

Main Methods:

• Treatment plans were generated for 20 intracranial metastases using Novalis Tx, including DCA, VMAT, and SIB-VMAT.
• Prescribed dose was 35 Gy in 5 fractions to the planning target volume (PTV).
• Dose escalation to 40 Gy and 45 Gy was performed using SIB-VMAT on a shrunk PTV-boost, with plans compared using conformity indices and dose-volume metrics for normal brain.

Main Results:

• SIB-VMAT demonstrated superior dose conformity (Paddick CI: 0.89-0.91) compared to DCA (0.78).
• SIB-VMAT significantly reduced healthy tissue overdosage (HTOF: 0.006-0.011) compared to DCA (0.118).
• VMAT and SIB-VMAT plans showed reduced volumes of normal brain receiving high doses (V30, V20, V10) compared to DCA.

Conclusions:

• SIB-VMAT significantly improves dose conformity to the planning target volume in intracranial stereotactic radiotherapy.
• SIB-VMAT effectively reduces high and low dose volumes in normal brain tissue compared to DCA.
• The high conformity of SIB-VMAT facilitates safe dose escalation for intracranial stereotactic radiotherapy.