Dosimetric comparison between RapidArc and HyperArc in hippocampal-sparing whole-brain radiotherapy with a simultaneous integrated boost

Jeongho Kim; Tae Gyu Kim; Byungdo Park; Hyunjung Kim; Yun Gyu Song; Hyoun Wook Lee; Young Zoon Kim; Jun Ho Ji; Seok-Hyun Kim; Sung Min Kim; Jun Ho Lee; Haeyoung Kim

doi:10.1016/j.meddos.2023.08.007

Dosimetric comparison between RapidArc and HyperArc in hippocampal-sparing whole-brain radiotherapy with a simultaneous integrated boost

Med Dosim. 2023 Sep 15:S0958-3947(23)00072-9. doi: 10.1016/j.meddos.2023.08.007. Online ahead of print.

Authors

Jeongho Kim¹, Tae Gyu Kim², Byungdo Park¹, Hyunjung Kim¹, Yun Gyu Song³, Hyoun Wook Lee⁴, Young Zoon Kim⁵, Jun Ho Ji⁶, Seok-Hyun Kim⁶, Sung Min Kim⁶, Jun Ho Lee⁷, Haeyoung Kim⁸

Affiliations

¹ Departments of Radiation Oncology, Samsung Changwon Hospital, Sungkyunkwan University School of Medicine, Changwon, South Korea.
² Departments of Radiation Oncology, Samsung Changwon Hospital, Sungkyunkwan University School of Medicine, Changwon, South Korea. Electronic address: tg1.kim@samsung.com.
³ Departments of Radiology, Samsung Changwon Hospital, Sungkyunkwan University School of Medicine, Changwon, South Korea.
⁴ Departments of Pathology, Samsung Changwon Hospital, Sungkyunkwan University School of Medicine, Changwon, South Korea.
⁵ Departments of Neurosurgery, Samsung Changwon Hospital, Sungkyunkwan University School of Medicine, Changwon, South Korea.
⁶ Departments of Internal Medicine, Samsung Changwon Hospital, Sungkyunkwan University School of Medicine, Changwon, South Korea.
⁷ Departments of Surgery, Samsung Changwon Hospital, Sungkyunkwan University School of Medicine, Changwon, South Korea.
⁸ Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea.

PMID: 37718172
DOI: 10.1016/j.meddos.2023.08.007

Abstract

The HyperArc technique is known for generating high-quality radiosurgical treatment plans for intracranial lesions or hippocampal-sparing whole-brain radiotherapy (WBRT). However, there is no reported feasibility of using the HyperArc technique in hippocampal-sparing WBRT with a simultaneous integrated boost (SIB). This study aimed to compare dosimetric parameters of 2 commercially-available volumetric-modulated arc radiotherapy techniques, HyperArc and RapidArc, when using hippocampal-sparing WBRT with a SIB to treat brain metastases. Treatment plans using HyperArc and RapidArc techniques were generated retrospectively for 19 previously treated patients (1 to 3 brain metastases). The planning target volumes for the whole brain (excluding the hippocampal avoidance region; PTV_WB) and metastases (PTV_met) were prescribed 25 and 45 Gy, respectively, in 10 fractions. Each plan included homogeneous and inhomogeneous delivery to the PTV_met. Dosimetric parameters for the target (conformity index [CI], homogeneity index [HI], target coverage [D_95%]), and nontarget organs at risk were compared for the HyperArc and RapidArc plans. For homogeneous delivery, dosimetric parameters, including mean CI, HI, and target coverage in PTV_WB and PTV_met, were superior for HyperArc than RapidArc plans (all p < 0.01). The PTV_WB and PTV_met target coverage for HyperArc plans was significantly greater than for RapidArc plans (96.17% vs 93.38%, p < 0.01; 94.02% vs 92.21%, p < 0.01, respectively). HyperArc plans had significantly lower mean hippocampal D_max and D_min values than RapidArc plans (D_max: 15.53 Gy vs, 16.71 Gy, p < 0.01; D_min: 8.33 Gy vs 8.93 Gy, p < 0.01, respectively). Similarly, inhomogeneous delivery of hyperArc produced a superior target and lower hippocampal dosimetric parameters than RapidArc, except for the HI of PTV_met (all p < 0.01). HyperArc generated superior conformity and target coverage with lower hippocampal doses than RapidArc. HyperArc could be an attractive technique for hippocampal-sparing WBRT with an SIB.

Keywords: Hippocampus; HyperArc; Simultaneous integrated boost; Whole-brain radiation therapy.