Volumetric Modulated Arc Radiotherapy for Early Stage Non-Small-Cell Lung Carcinoma: Is It Better Than the Conventional Static Beam Intensity Modulated Radiotherapy?
This study compared the performance of volumetric modulated arc therapy (VMAT) techniques: single arc volumetric modulated arc therapy (SA-VMAT) and double arc volumetric modulated arc therapy (DA-VMAT) with the static beam conventional intensity modulated radiotherapy (C-IMRT) for non-small-cell lung carcinoma (NSCLC). Twelve stage I and II NSCLC patients were recruited and their planning CT with contoured planning target volume (PTV) and organs at risk (OARs) was used for planning. Using the same dose constraints and planning objectives, the C-IMRT, SA-VMAT, and DA-VMAT plans were optimized. C-IMRT consisted of 7 static beams, while SA-VMAT and DA-VMAT plans consisted of one and two full gantry rotations, respectively. No significant difference was found among the three techniques in target homogeneity and conformity. Mean lung dose in C-IMRT plan was significantly lower than that in DA-VMAT plan . The ability of OAR sparing was similar among the three techniques, with no significant difference in V20, V10, or V5 of normal lungs, spinal cord, and heart. Less MUs were required in SA-VMAT and DA-VMAT. Besides, SA-VMAT required the shortest beam on time among the three techniques. In treatment of early stage NSCLC, no significant dosimetric superiority was shown by the VMAT techniques over C-IMRT and DA-VMAT over SA-VMAT. 1. Introduction Lung cancer is currently the most common cancer in the world and accounted for 16.8% of all cancer incidence and 28.8% of all cancer deaths in Hong Kong in 2010 [1]. Approximately 75% of all lung cancers belong to non-small-cell lung carcinoma (NSCLC) [2]. For patients with inoperable disease, a 6-7 week course of radiation therapy (RT) with or without chemotherapy is the standard treatment [3]. It has been proven that increasing the dose to the target results in better local control and survival in patients with NSCLC [4, 5]. However, conventional radiotherapy techniques often experience difficulty in dose escalation due to the inadequacy in sparing the adjacent normal tissues such as the surrounding normal lung tissue [6, 7]. The situation has now been improved with the recent introduction of the more advanced radiotherapy technologies such as the intensity modulated radiotherapy (IMRT). IMRT controls the intensity of individual beamlets across a radiation beam using the dynamic multileaf collimator (MLC) and delivers conformal dose to the target. Volumetric modulated radiotherapy (VMAT) is an advanced form of IMRT in which the gantry rotates round the patient during treatment in addition to the moving MLC. The main
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