Author(s)

Wu Wang¹, Didi Chen², Ce Han², Xiaomin Zheng², Yongqiang Zhou², Changfei Gong², Congying Xie^2*, Xiance Jin^2*

¹Medical Engineering Department, The 1st Affiliated Hospital of Wenzhou Medical University, Wenzhou, China.
²Radiation and Medical Oncology Department, The 1st Affiliated Hospital of Wenzhou Medical University, Wenzhou, China.

Purpose: To investigate the feasibility of partial arc volumetric modulated arc therapy (VMAT) in lung cancer stereotactic body radiotherapy (SBRT), as well the volumetric and dosimetric effects of different internal target volume (ITV) definitions with 4D CT. Methods: Fourteen patients with primary and metastatic lung cancer underwent SBRT were enrolled. Full and partial arc VMAT plans were generated with four different ITVs: ITV_all, ITV_MIP, ITV_AIP and ITV_2phases, representing ITVs generated from all 10 respiratory phases, maximum intensity projection (MIP), average intensity projection (AIP), and 2 extreme respiratory phases. Volumetric and dosimetric differences, as well as MU and delivery time were investigated. Results: Partial arc VMAT irradiated more dose at 2 cm away from planning target volume (PTV) (P = 0.002), however, it achieved better protection on mean lung dose , lung V5, spinal cord, heart and esophagus compared with full arc VMAT. The average MU and delivery time of partial arc VMAT were 240 and 1.6 min less than those of full arc VMAT. There were no significant differences on target coverage and organ at risks (OARs) sparing among four ITVs. The average percent volume differences of ITV_MIP, ITV_AIP and ITV_2phases to ITV_all were 8.6%, 13.4%, and 25.2%, respectively. Conclusions: Although partial arc VMAT delivered more dose 2 cm out of PTV, it decreases the dose to lung, spinal cord, and esophagus, as well decreased the total MU and delivery time compared with full arc VMAT without sacrificing target coverage. Partial arc VMAT was feasible and more efficient for lung SBRT.

Lung Cancer, Stereotactic Body Radiotherapy, Four Dimensional Computed Tomography, Internal Target Volume, Volumetric Modulated Arc Therapy

Wang, W. , Chen, D. , Han, C. , Zheng, X. , Zhou, Y. , Gong, C. , Xie, C. and Jin, X. (2018) Partial and Full Arc Volumetric Modulated Arc Therapy in Lung Cancer Stereotactic Body Radiotherapy with Different Definitions of Internal Target Volume Based on 4D CT. International Journal of Medical Physics, Clinical Engineering and Radiation Oncology, 7, 491-502. doi: 10.4236/ijmpcero.2018.74042.