A comparison of three different VMAT techniques for the delivery of lung stereotactic ablative radiation therapy

Abstract

IntroductionThe purpose of this study was to investigate coplanar and non‐coplanar volumetric modulated arc therapy (VMAT) delivery techniques for stereotactic ablative radiation therapy (SABR) to the lung.MethodsFor ten patients who had already completed a course of radiation therapy for early stage lung cancer, three new SABR treatment plans were created using (1) a coplanar full arc (FA) technique, (2) a coplanar partial arc technique (PA) and (3) a non‐coplanar technique utilising three partial arcs (NCA). These plans were evaluated using planning target volume (PTV) coverage, dose to organs at risk, and high and intermediate dose constraints as incorporated by radiation therapy oncology group (RTOG) 1021.ResultsWhen the FA and PA techniques were compared to the NCA technique, on average the PTV coverage (V 54Gy) was similar (P = 0.15); FA (95.1%), PA (95.11%) and NCA (95.71%). The NCA resulted in a better conformity index (CI) of the prescription dose (0.89) when compared to the FA technique (0.88, P = 0.23) and the PA technique (0.83, P = 0.06). The NCA technique improved the intermediate dose constraints with a statistically significant difference for the D 2cm and R 50% when compared with the FA (P < 0.03 and <0.0001) and PA (P < 0.04 and <0.0001) techniques. The NCA technique reduced the maximum spinal cord dose by 2.72 and 4.2 Gy when compared to the PA and FA techniques respectively. Mean lung doses were 4.09, 4.31 and 3.98 Gy for the FA, PA and NCA techniques respectively.ConclusionThe NCA VMAT technique provided the highest compliance to RTOG 1021 when compared to coplanar techniques for lung SABR. However, single FA coplanar VMAT was suitable for 70% of patients when minor deviations to both the intermediate dose and organ at risk (OAR) constraints were accepted.

Non-coplanar VMAT plans for lung SABR to reduce dose to the heart: a planning study

“…Fitzgerald et al compared three types of VMAT plans for lung SABR, which were coplanar full arc (CFA), coplanar partial arc (CPA), and non-coplanar partial arc (NPA) VMAT plans. 4 They demonstrated that the NPA plans improved conformity of the PTVs while reducing irradiation of body by intermediate doses as well as the maximum doses to spinal cord. In that study, the locations of the target volumes were various in both lungs and the number of cases analyzed in that study was limited (10 cases); therefore, a deep analysis on the benefit of the NPA plans could not be performed.…”

“…1,2 To achieve high local control rate and low toxicity of lung SABR, various treatment planning techniques utilizing non-coplanar beams were proposed and investigated to acquire an optimal dose distributions. [3][4][5][6][7] Dong et al proposed 4π non-coplanar plans to reduce doses to organs at risk (OARs), while improving planning target volume (PTV) coverage for centrally located or large lung tumors. 3 They showed superior plan quality to that of volumetric modulated arc therapy (VMAT) with two full arcs.…”

“…7 Various studies were performed on the NPA VMAT plans for lung SABR and comprehensively reviewing the results of the previous studies, the NPA VMAT might be selectively beneficial for lung SABR with tumors at specific locations in the lung when combining particular gantry rotations and couch angles appropriately. [3][4][5][6][7] For example, lung SABR with tumors located close to heart might take advantage of NPA VMAT plans, which is a challenging case to deliver a prescription dose to the target volume while keeping doses to heart less than the tolerance level because of the proximity of the heart to the target volume. 8 However, to the best of our knowledge, no study has investigated this yet.…”

Technical know‐how in stereotactic ablative radiotherapy (SABR)

“…Fitzgerald et al. reported their experience with 3DCRT and VMAT at this journal issue . The CyberKnife (Accuray, Sunnyvale, CA) system has a unique treatment planning system based on robotically directed beam delivery.…”

Dosimetric comparison of coplanar and noncoplanar beam arrangements for radiotherapy of patients with lung cancer: A meta‐analysis

“…recent studies, [4][5][6][7][8] SBRT has exhibited favorable clinical outcomes. To achieve a high local control rate and a low toxicity, SBRT treatment of the lung cancer has been performed on gantry-mounted linear accelerators (LINACs) using noncoplanar or coplanar three-dimensional conformal radiation therapy (3DCRT), 9,10 intensity modulated radiation therapy (IMRT), 10,11 and volumetric modulated arc therapy (VMAT) [12][13][14] to acquire optimal dose distributions [15][16][17][18] and increase the efficiency of treatment delivery.…”