AUTHOR=Xue Juan , Jin Sunian , Zhang Hongtao , Zou Kun , Sheng Junxiu , Tang Jinhai , Zhao Wanying , Yang Ping , Tang Lufan , Lv Xiupeng , Lv Li 

TITLE=A simplified non-coplanar volumetric modulated arc therapy for the whole brain radiotherapy with hippocampus avoidance

JOURNAL=Frontiers in Oncology

VOLUME=13

YEAR=2023

URL=https://www.frontiersin.org/journals/oncology/articles/10.3389/fonc.2023.1143564

DOI=10.3389/fonc.2023.1143564

ISSN=2234-943X

ABSTRACT=<sec><title>Purpose</title><p>To evaluate the feasibility of using a simplified non-coplanar volumetric modulated arc therapy (NC-VMAT) and investigate its dosimetric advantages compared with intensity modulated radiation therapy (IMRT) and coplanar volumetric modulated arc therapy (C-VMAT) for hippocampal-avoidance whole brain radiation therapy (HA-WBRT).</p></sec><sec><title>Methods</title><p>Ten patients with brain metastase (BM) were included for HA-WBRT. Three treatment plans were generated for each case using IMRT, C-VMAT, and NC-VMAT, respectively.</p></sec><sec><title>Results</title><p>The dosimetric results of the three techniques complied roughly with the RTOG 0933 criteria. After dose normalization, the V<sub>30Gy</sub> of whole brain planned target volume (WB-PTV) in all the plans was controlled at 95%. Homogeneity index (HI) of WB-PTV was significantly reduced in NC-VMAT (0.249 ± 0.017) over IMRT (0.265 ± 0.020, <italic>p</italic>=0.005) and C-VMAT (0.261 ± 0.014, <italic>p</italic>=0.020). In terms of conformity index (CI), NC-VMAT could provide a value of 0.821 ± 0.010, which was significantly superior to IMRT (0.788 ± 0.019, <italic>p</italic>&lt;0.001). According to D<sub>2%</sub> of WB-PTV, NC-VMAT could provide a value of 35.62 ± 0.37Gy, significantly superior to IMRT (36.43 ± 0.65Gy, <italic>p</italic>&lt;0.001). According to D<sub>50%</sub> of WB-PTV, NC-VMAT can achieve the lowest value of 33.18 ± 0.29Gy, significantly different from IMRT (33.47 ± 0.43, <italic>p</italic>=0.034) and C-VMAT (33.58 ± 0.37, <italic>p</italic>=0.006). Regarding D<sub>2%</sub>, D<sub>98%</sub>, and D<sub>mean</sub> of hippocampus, NC-VMAT could control them at 15.57 ± 0.18Gy, 8.37 ± 0.26Gy and 11.71 ± 0.48Gy, respectively. D<sub>2%</sub> and D<sub>mean</sub> of hippocampus for NC-VMAT was significantly lower than IMRT (D<sub>2%</sub>: 16.07 ± 0.29Gy, <italic>p</italic>=0.001 D<sub>mean</sub>: 12.18 ± 0.33Gy, <italic>p</italic>&lt;0.001) and C-VMAT (D<sub>2%</sub>: 15.92 ± 0.37Gy, <italic>p</italic>=0.009 D<sub>mean</sub>: 12.21 ± 0.54Gy, <italic>p</italic>&lt;0.001). For other organs-at-risk (OARs), according to D<sub>2%</sub> of the right optic nerves and the right lenses, NC-VMAT had the lowest values of 31.86 ± 1.11Gy and 7.15 ± 0.31Gy, respectively, which were statistically different from the other two techniques. For other organs including eyes and optic chiasm, NC-VMAT could achieve the lowest doses, different from IMRT statistically.</p></sec><sec><title>Conclusion</title><p>The dosimetry of the three techniques for HA-WBRT could roughly comply with the proposals from RTOG 0933. After dose normalization (D<sub>95%</sub>=30Gy), NC-VMAT could significantly improve dose homogeneity and reduce the D<sub>50%</sub> in the brain. Besides, it can reduce the D<sub>2%</sub> of the hippocampus, optic nerves, and lens. With this approach, an efficient and straightforward plan was accomplished.</p></sec>