Treatment plan comparison of volumetric‐modulated arc therapy to intensity‐modulated radiotherapy in lung stereotactic body radiotherapy using either 6‐ or 10‐MV photon energies

PURPOSE: The aim of this study was to dosimetrically compare volumetric‐modulated arc therapy (VMAT) with intensity‐modulated radiotherapy (IMRT) techniques using either 6‐ or 10‐MV photon beam energies in lung stereotactic body radiation therapy (SBRT) plans. METHODS: Thirty patients with primary or metastatic lung tumors eligible for SBRT were randomly selected. VMAT and IMRT treatment plans using either 6‐ or 10‐MV photon energies were generated through automatic SBRT planning software in the RayStation treatment planning system. RESULTS: For planning target volume, there was no difference in D (95%) for all plans, whereas D (2%) and D (50%) were significantly increased by 5.22%–5.98% and 2.47%–2.59%, respectively, using VMAT(6/10‐MV) plans compared to IMRT(6/10‐MV) plans. When comparing the D (max) of organs at risk (OARs), VMAT(6/10‐MV) was 18.32%–47.95% lower than IMRT(6/10‐MV) for almost all OARs. VMAT(6/10‐MV) obviously decreased D (mean), V (5Gy), V (10Gy), and V (20Gy) of whole lung by 9.68%–20.92% than IMRT(6/10‐MV). Similar results were found when comparing VMAT(6‐MV) with IMRT(10‐MV) or VMAT(10‐MV) with IMRT(6‐MV). The differences in the D (2%), heterogeneity index, and conformity index between 6‐ and 10‐MV plans are not statistically significant. Plans using 6‐MV performed 4.68%–8.91% lower levels of D (max) of spinal cord, esophagus, great vessels, and trachea and proximal bronchial tree than those using 10‐MV plans. Similarly, D (mean), V (5Gy), V (10Gy), and V (20Gy) of whole lung were also reduced by 2.79%–5.25% using 6‐MV. For dose fall‐off analysis, the D (2cm) and R (50%) of VMAT(6/10‐MV) were lower than those of IMRT(6/10‐MV). Dose fall‐off curve based on 10 rings was steeper for VMAT plans than IMRT plans regardless of the energy used. CONCLUSIONS: For lung SBRT plans, VMAT‐based plans significantly reduced OARs dose and steepened dose fall‐off curves compared to IMRT‐based plans. A 6‐MV energy level was a better choice than 10‐MV for lung SBRT. In addition, the dose differences between different techniques were more obvious than those between different energy levels.