Introduced in 2017 to help simplify SRS treatment planning and delivery for multiple brain metastases, HyperArc high-definition radiosurgery is now proving effective at treating benign intracranial lesions.
HyperArc® high-definition radiotherapy from Varian was designed and optimized for intracranial central nervous system (CNS) radiosurgery applications. As previously reported, medical physicists around the world are finding dosimetric advantages with HyperArc over conventional SRS in target conformity and dose gradients. Now, recent publications show that HyperArc can be a viable approach for treating other intracranial targets including benign brain tumors such as acoustic neuromas and meningiomas.
According to Raymond Schulz, Senior Global Manager of Radiosurgery in the Office of Medical Affairs at Varian, two specific features of HyperArc make it particularly suited for treating these targets. “The SRS-normal tissue objective algorithm (SRS-NTO) ensures steep dose gradients, which mitigate any dose-bridging effect, and keeps the dose to normal tissues low. Secondly, HyperArc planning efficiencies make it a viable—and practical—choice for addressing these types of targets,” he said.
Whole-Brain Radiotherapy with Hippocampal Sparing
One particularly interesting application of HyperArc is for patients who are receiving whole-brain radiotherapy (WBRT).
“While there is now prospective evidence supporting the use of radiosurgery for focused treatment of four or more metastases instead of WBRT1, for some patients the latter will still be the preferred treatment modality,” said David James, Varian’s Senior Marketing Manager for Radiosurgery in EMEA. “Reducing dose to the hippocampus is critical to avoid neurocognitive deterioration. For these cases, data are emerging that suggest that HyperArc can be used without the SRS-NTO algorithm to provide treatment plans with improved hippocampal sparing compared to conventional techniques.”
A study in ten patients by Sprowls et al2 evaluating HyperArc for WBRT with hippocampal sparing following RTOG 0933 dosimetric criteria concluded: “The primary advantages of WBRT with hippocampal sparing using HyperArc, compared to coplanar VMAT, are the gains in OAR sparing and reduced high dose volumes to the PTV, while still fully complying with RTOG dosimetric criteria.”
HyperArc Plans for Skull-Based Meningiomas
In a study that evaluated HyperArc treatment planning for skull-based meningiomas, Snyder et al3 report: “HyperArc can be beneficial both in treatment planning by using the SRS-NTO and in delivery efficiency through the decrease in monitor units and automated delivery.” This team used a multicriteria optimization algorithm when developing their HyperArc treatment plans.
Bossart et al4 looked at HyperArc plans for a spectrum of cancerous and benign brain lesions including ten base-of-skull meningiomas, acoustic neuromas, and pituitary adenomas. This team compared HyperArc plans with plans for patients previously treated using a GammaKnife® (GK) Perfexion system. They found that the HyperArc plans compared positively to GK plans when using a high-definition multileaf collimator (HDMLC).
Since it was first deployed, HyperArc has been installed at over 165 treatment sites around the world and has been used to treat over 10,000 patients representing 30,000 targets. “As more cancer centers around the world develop programs for treating new indications or replace existing SRS techniques with HyperArc on TrueBeam® or Edge® systems, we fully anticipate that studies will continue to accrue showing that HyperArc enables high-quality SRS treatment for brain tumors, multiple mets, and other types of intracranial targets, benign and cancerous,” said Schulz. “In the past three years, more than 30 papers have been published by cancer institutions around the world demonstrating the quality characteristics and flexibility of the HyperArc high-definition radiotherapy system.”
1Li J, Ludmir EB, Wang Y et al. Stereotactic Radiosurgery versus Whole-brain Radiation Therapy for Patients with 4-15 Brain Metastases: A Phase III Randomized Controlled Trial. Int J Radiat Oncol Biol Phys. 2020; 108:3, S21 - S22.
2Sprowls, CJ, Shah AP, Kelly P et al. Whole brain radiotherapy with hippocampal sparing using Varian HyperArc. Med Dosim. 2021;46(3):264-268.
3Snyder KC, Cunningham J, Huang Y, et al. Dosimetric Evaluation of Fractionated Stereotactic Radiation Therapy for Skull Base Meningiomas Using HyperArc and Multicriteria Optimization. Adv Radiat Oncol. 2021;6(4):100663. Published 2021 Feb 6.
4Bossart E, Mellon EA, Monterroso I et al. Assessment of single isocenter linear accelerator radiosurgery for metastases and base of skull lesions. Phys Med. 2021 Jan;81:1-8.