Total-body irradiation using linac-based volumetric modulated arc therapy: Its clinical accuracy, feasibility and reliability

• Published in: Radiotherapy and oncology 2018-12, Vol.129 (3), p.527-533
• Main Authors: Tas, Bora, Durmus, Ismail Faruk, Okumus, Ayse, Uzel, Omer Erol, Gokce, Muge, Goksoy, Hasan Sami, Ozsahin, Esat Mahmut
• Format: Article
• Language: English
• Subjects: DVH-based 3D patient QA; TBI; VMAT
• ISSN: 0167-8140; 1879-0887
• DOI: 10.1016/j.radonc.2018.08.005

•TBI is an important part of conditioning regimens in patients undergoing BMT.•Linac-based VMAT TBI technique can increase the dose homogeneity and conformality compared to classical extended-SSD TBI techniques.•High precision in patient positioning and dose delivery, less toxicity for specific organs at risk, and patient comfort can be achieved.•DVH-based 3D dose verification QA is possible with linac-based VMAT TBI. 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 lymphoblastic leukemia (ALL). 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. 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. 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 differences between planned and delivered doses. It is feasible, accurate, and reliable.