Plan quality comparison between 4-arc and 6-arc noncoplanar volumetric modulated arc stereotactic radiotherapy for the treatment of multiple brain metastases

Kotaro Yoshio, Toshiharu Mitsuhashi, Akihisa Wakita, Takahiro Kitayama, Kento Hisazumi, Daisaku Inoue, Tsuyoki Shiode, Shiro Akaki, Susumu Kanazawa

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

To compare the plans of 4-arc and 6-arc noncoplanar volumetric modulated arc stereotactic radiotherapy (VMA-SRT) for multiple brain metastases and to investigate the cutoff value for the tumor number and volume for 6-arc rather than 4-arc VMA-SRT. We identified 24 consecutive multiple-target cases (3 to 19 targets in each case) with 189 total targets. We constructed plans using both 4- and 6-arc noncoplanar VMA-SRT. The prescribed dose was 36 Gy/6 fr, and it was delivered to 95% of the planning target volume (PTV). The plans were evaluated for the dose conformity using the Radiation Therapy Oncology Group and Paddick conformity indices (RCI and PCI), fall-off (Paddick gradient index [PGI]), and the normal brain dose. The median (range) RCI, PCI, and PGI was 0.94 (0.92 to 0.99), 0.89 (0.77 to 0.94), and 3.75 (2.24 to 6.54) for the 4-arc plan and 0.94 (0.91 to 0.98), 0.89 (0.76 to 0.94), and 3.65 (2.24 to 6.5) for the 6-arc plan, respectively. The median (range) of the normal brain dose was 910.3 cGy (381.4 to 1268.9) for the 4-arc plan and 898.8 cGy (377 to 1252.9) for the 6-arc plan. The PGI of the 6-arc plan was significantly superior to that of the 4-arc plan (p = 0.0076), and the optimal cutoff values for the tumor number and volume indicative of 6-arc (and not 4-arc) VMA-SRT were cases with ≥ 5 metastases and a PTV of ≥ 12.9 mL, respectively. The PCI values, however, showed no significant difference between the 2 plans. We believe these results will help in considering the use of 6-arc VMA-SRT for multiple brain metastases.

Original languageEnglish
Pages (from-to)358-362
Number of pages5
JournalMedical Dosimetry
Volume43
Issue number4
DOIs
Publication statusPublished - Dec 1 2018

Keywords

  • Brain metastases
  • Noncoplanar arc
  • Stereotactic radiotherapy
  • Volumetric modulated arc therapy

ASJC Scopus subject areas

  • Radiological and Ultrasound Technology
  • Oncology
  • Radiology Nuclear Medicine and imaging

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