Original article Total-body irradiation using linac-based volumetric modulated arc therapy: Its clinical accuracy, feasibility and reliability Bora Tas a,⇑ , Ismail Faruk Durmus a , Ayse Okumus a , Omer Erol Uzel a , Muge Gokce b , Hasan Sami Goksoy b , Esat Mahmut Ozsahin c a Department of Radiation Oncology; b Department of Hematology, Yeni Yuzyil University Gaziosmanpasa Hospital, Istanbul, Turkey; c Department of Radiation Oncology, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland article info Article history: Received 12 March 2018 Received in revised form 2 August 2018 Accepted 3 August 2018 Available online xxxx Keywords: DVH-based 3D patient QA VMAT TBI abstract Purpose: To report the feasibility, accuracy, and reliability of volumetric modulated arc therapy (VMAT)- based total-body irradiation (TBI) treatment in patients with acute myeloid leukemia (AML) or acute lym- phoblastic leukemia (ALL). Materials and methods: From 2015 to 2018, 30 patients with AML or ALL were planned and treated with VMAT-based TBI, which consisted of three isocenters and three overlapping arcs. TBI dose was prescribed to 90% of the planning treatment volume (PTV) receiving 12 Gy in six fractions, at two fractions per day. Mean lung and kidney doses were restricted less than 10 Gy, and maximum lens dose less than 6 Gy. Quality assurance (QA) comprised the verification of the irradiation plans via dose–volume histogram (DVH) based 3D patient QA system. Results: Average mean lung dose was 9.7 ± 0.2 Gy, mean kidney dose 9.6 ± 0.2 Gy, maximum lens dose 4.5 ± 0.4 Gy, mean PTV dose 12.7 ± 0.1 Gy, and heterogeneity index of PTV was 1.16 ± 0.02 in all patients. Grade 3 or more acute radiation toxicity was not observed. When comparing plan and DVH-based 3D patient QA results, average differences of 3.3% ± 1.3 in mean kidney doses, 1.1% ± 0.7 in mean lung doses, and 0.9% ± 0.4 in mean target doses were observed. Conclusion: Linac-based VMAT increased the dose homogeneity of TBI treatment more than extended SSD techniques. Partial cone-beam CT and optical surface-guided system assure patient positioning. DVH-based 3D patient dose verification QA was possible with linac-based VMAT showing small differ- ences between planned and delivered doses. It is feasible, accurate, and reliable. Ó 2018 Elsevier B.V. All rights reserved. Radiotherapy and Oncology xxx (2018) xxx–xxx Radiation therapy (RT) in the form of total-body irradiation (TBI) technique continues to be an important part of conditioning regimens in patients undergoing bone-marrow transplantation (BMT) in hematological malignancies. TBI implemented using megavoltage photon beams is a conditioning modality used in treating several diseases, including multiple myeloma, leukemias, lymphomas, and some solid tumors [1,2]. Studies in mice and humans show that the toxicities of TBI can be improved further by fractionating the radiation dose [3,4]. A randomized study from Seattle in the setting of AML compared single-dose TBI (10 Gy) to a fractionated schedule (12 Gy in 6 fractions). The last update of this trial showed significant superiority of the fractionated scheme in terms of event-free survival [5]. Most of the current methods follow the recommendations of the European Group for Blood and Marrow Transplantation (EBMT) [6], which suggest to check the dose homogeneity along the patient’s midline at several points and to specify the lung dose at a point, which is representative for more than 50% of the lung volume. Most of the current TBI proce- dures are based on techniques established on linear accelerators used for conventional RT. Large photon fields are generally achieved by treating the patient at extended skin-surface distance (SSD) with standard linear accelerators or with special dedicated machines. Equipment Guidelines recommend the use of parallel- opposed pairs of high-energy photon beams from 4 to 18 MV for TBI [2]. Classic TBI has a long application time, non-conformality of beam-application with the inability to individually spare organs at risk (OARs) and hence, its acute and late toxicity [7–11]. The use of an inverse optimization algorithm improves the dose homo- geneity in comparison to conventional forward planned tech- niques. The large target size hampers the use of modern methods for linear accelerator of radiation oncology. Individually implemented RT improves the dose distribution on target structures and organs at risk (OAR) more than extended SSD https://doi.org/10.1016/j.radonc.2018.08.005 0167-8140/Ó 2018 Elsevier B.V. All rights reserved. ⇑ Corresponding author at: Department of Radiation Oncology, Yeni Yuzyil University Gaziosmanpasa Hospital, Merkez mah Cukurcesme cad No: 51, Gazios- manpasa, 34245 Istanbul, Turkey. E-mail address: bora_tash@yahoo.com (B. Tas). Radiotherapy and Oncology xxx (2018) xxx–xxx Contents lists available at ScienceDirect Radiotherapy and Oncology journal homepage: www.thegreenjournal.com Please cite this article in press as: Tas B et al. Total-body irradiation using linac-based volumetric modulated arc therapy: Its clinical accuracy, feasibility and reliability. Radiother Oncol (2018), https://doi.org/10.1016/j.radonc.2018.08.005