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

Abstract

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.

Keywords: intensity-modulated radiotherapy (IMRT); lung cancer; radiotherapy; stereotactic body radiotherapy (SBRT); volumetric-modulated arc therapy (VMAT).