title: Impact of volumetric modulated arc therapy technique on treatment with partial breast irradiation.
abstract: OBJECTIVE
  To investigate the technical feasibility of volumetric modulated arc therapy (V-MAT) in the delivery of partial breast irradiation (PBI).
  
  
  METHODS
  V-MAT and the standard, three-dimensional conformal radiotherapy (3D-CRT), were compared retrospectively in 8 patients previously treated with PBI. These patients' plans were replanned with a single partial arc using V-MAT that included partial blocking to minimize normal tissue dose. Dosimetric parameters were calculated to evaluate plan quality. Quality assurance studies included verifying both the point and the multiple planar doses. Total monitor units and delivery time were also evaluated, and collision clearance was analyzed.
  
  
  RESULTS
  Volumes of ipsilateral lung irradiated to 10 Gy (V10) and 20 Gy (V20) by V-MAT were significantly less than those of 3D-CRT (p = 0.03 for V10 and p = 0.025 for V20). The volume of ipsilateral breast irradiated to 5 Gy was significantly less by using V-MAT than with 3D-CRT (p = 0.02), with a ratio of integrated dose of <1.00. The total mean monitor units (489 +/- 38) for V-MAT were significantly less than those for 3D-CRT (634 +/- 123) (p = 0.017), with a 23% reduction. The average machine delivery time was 1.21 +/- 0.10 min for the V-MAT plans and 6.28 +/- 1.40 min for the 3D-CRT plans, resulting in a reduction factor of 80.1%. The conformity indexes were 1.3 in the V-MAT plans and 1.5 in the 3D-CRT plans (p = 0.102).
  
  
  CONCLUSIONS
  V-MAT technology is feasible for PBI patients. Compared to a conventional 3D-CRT technique, it is more efficient, offers equivalent or better dose conformity, delivers lower doses to the ipsilateral lung and breast, and may potentially reduce intrafractional motion.
authors.affiliation: Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina, USA. jian-jian.qiu@duke.edu
authors.forename: Jian-Jian
authors.initials: JJ
authors.lastname: Qiu
authors.forename: Zheng
authors.initials: Z
authors.lastname: Chang
authors.forename: Q Jackie
authors.initials: QJ
authors.lastname: Wu
authors.forename: Sua
authors.initials: S
authors.lastname: Yoo
authors.forename: Janet
authors.initials: J
authors.lastname: Horton
authors.forename: Fang-Fang
authors.initials: FF
authors.lastname: Yin
mesh_terms: D001940:Breast / Q000528:radiation effects; D001943:Breast Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy* / Q000601:surgery; D005240:Feasibility Studies; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging / Q000528:radiation effects; D006801:Humans; D008168:Lung / Q000528:radiation effects; D015412:Mastectomy, Segmental; D011832:Radiation Injuries / Q000517:prevention & control; D011859:Radiography; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D020266:Radiotherapy, Conformal / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012189:Retrospective Studies; D013997:Time Factors