Tumor Control and Toxicity in Benign Intracranial Tumors Treated with HyperArc Radiosurgery

Overview

This study evaluates the efficacy and safety of HyperArc™ frameless linac-based radiosurgery for benign intracranial tumors. Results demonstrate high-quality treatment planning with precise dose delivery, achieving optimal tumor control while minimizing toxicity to critical brain structures.

Background

Radiosurgery is a standard treatment for benign intracranial tumors, traditionally delivered via GammaKnife or CyberKnife systems. These modalities use point-and-shoot geometries, which are less efficient than arc-based delivery methods. HyperArc™, an automated single-isocenter volumetric modulated arc therapy (VMAT) system, offers improved plan quality and delivery efficiency. Its effectiveness for benign intracranial tumors without additional planning target volume margins remains to be fully characterized.

Data Highlights

Patients treated between May 2018 and October 2021 underwent HyperArc™ radiosurgery with no additional PTV margin. Treatment plans used 10 MV flattening filter-free beams with 2 to 4 arcs. Quality assurance showed median registration offset of 0.32 mm and imaging-treatment coordinate coincidence of 0.2 mm. Intrafraction motion was monitored continuously, with translational errors mostly under 0.5 mm. Tumor control and toxicity outcomes were assessed with follow-up imaging beyond 3 months.

Key Findings

• HyperArc™ enabled automated, high-quality radiosurgery plans with excellent conformity and steep dose gradients.
• Full prescription dose was normalized to ≥ 99% of the gross tumor volume without additional PTV expansion.
• Quality assurance confirmed submillimeter geometric accuracy and precise dose delivery.
• Intrafraction motion monitoring ensured minimal patient movement during treatment.
• Tumors near critical structures were identified based on proximity and dose thresholds to brainstem, optic apparatus, and cochlea.
• Early clinical outcomes suggest effective tumor control with minimal toxicity in benign intracranial tumors treated using this frameless linac system.

Clinical Implications

HyperArc™ radiosurgery provides a safe and efficient alternative to traditional radiosurgery platforms for benign intracranial tumors, allowing for precise dose delivery without additional PTV margins. Continuous motion monitoring and rigorous quality assurance protocols are essential to maintain treatment accuracy and minimize toxicity. This approach may improve workflow and patient comfort due to frameless immobilization.

Conclusion

HyperArc™ frameless linac-based radiosurgery achieves high-quality tumor control with minimal toxicity in benign intracranial tumors, supporting its use as an effective treatment modality. Further long-term follow-up will clarify durability of tumor control and late toxicity profiles.

References

1. Varian Medical Systems Inc. -- HyperArc™ Radiosurgery System
2. Paddick I. -- Conformity and Gradient Indices in Radiosurgery
3. American Association of Physicists in Medicine Task Group 142 -- Quality Assurance Guidelines