title: Use of volumetric-modulated arc therapy for treatment of Hodgkin lymphoma.
abstract: To evaluate volumetric-modulated arc therapy (VMAT) for treatment of Hodgkin lymphoma (HL) in patients where conventional radiotherapy was not deliverable. A planning computed tomography (CT) scan was acquired for a twelve-year-old boy with Stage IIIB nodular sclerosing HL postchemotherapy with positive positron emission tomography scan. VMAT was used for Phase 1 (19.8Gy in 11 fractions) and Phase 2 (10.8Gy in 6 fractions) treatment plans. Single anticlockwise arc plans were constructed using SmartArc (Philips Radiation Oncology Systems, Fitchburg, WI) with control points spaced at 4°. The inverse-planning objectives were to uniformly irradiate the planning target volume (PTV) with the prescription dose while keeping the volume of lung receiving greater than 20Gy (V20Gy) to less than 30% and minimize the dose to the other adjacent organs at risk (OAR). Pretreatment verification was conducted and the treatment delivery was on an MLCi Synergy linear accelerator (Elekta Ltd, Crawley, UK). The planning results were retrospectively confirmed in a further 4 patients using a single PTV with a prescribed dose of 19.8Gy in 11 fractions. Acceptable dose coverage and homogeneity were achieved for both Phase 1 and 2 plans while keeping the lung V20Gy at 22.5% for the composite plan. The beam-on times for Phase 1 and Phase 2 plans were 109 and 200 seconds, respectively, and the total monitor units were 337.2MU and 292.5MU, respectively. The percentage of measured dose points within 3% and 3mm for Phase 1 and Phase 2 were 92% and 98%, respectively. Both plans were delivered successfully. The retrospective planning study showed that VMAT improved PTV dose uniformity and reduced the irradiated volume of heart and lung, although the volume of lung irradiated to low doses increased. Two-phased VMAT offers an attractive option for large volume sites, such as HL, giving a high level of target coverage and significant OAR sparing together with efficient delivery.
authors.affiliation: Joint Department of Physics, Royal Marsden NHS Foundation Trust, Sutton, Surrey, UK. Electronic address: Young.Lee@rmh.nhs.uk.
authors.forename: Young K
authors.initials: YK
authors.lastname: Lee
authors.forename: James L
authors.initials: JL
authors.lastname: Bedford
authors.forename: Mary
authors.initials: M
authors.lastname: Taj
authors.forename: Frank H
authors.initials: FH
authors.lastname: Saran
mesh_terms: D002648:Child; D006689:Hodgkin Disease / Q000532:radiotherapy*; D006801:Humans; D008297:Male; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated
keywords: Dynamic arc therapy; Hodgkin lymphoma; Radiotherapy; VMAT; Volumetric-modulated arc therapy