title: Proton partial breast irradiation in the supine position: Treatment description and reproducibility of a multibeam technique.
abstract: OBJECTIVE
  Proton-accelerated partial breast irradiation (APBI) is early in its developmental phase without standardized treatment parameters. We report an approach to multibeam proton APBI using a universally available supine setup and deliberate beam arrangement strategy to limit the total area of skin receiving a full dose while being robust for interfraction variation.
  
  
  METHODS
  Thirty-three American Society for Radiation Oncology consensus-suitable/cautionary APBI candidates were treated using a passively scattered proton beam between 2010 and 2014 to 34 Gy relative biological effectiveness in 10 fractions twice daily. All patients were immobilized in a Vac-Lok cradle, typically with the arm down, and adducted to mound the breast and facilitate multiple, optimal en face beams. Radiopaque wires were placed on the surgical scar and 3 markers separate from the scar were placed elsewhere on the breast. All markers were used for each setup and removed before treatment. Marker displacement, wire rotation, and wire displacement were recorded from 10 random patients (100 orthogonal films). A 15-mm expansion was made to the tumor bed to obtain a clinical target volume, and followed by a 5-mm skin contraction and exclusion of the chest wall. A radial planning target volume margin of 5 mm was used.
  
  
  RESULTS
  Across 100 pretreatment images, median displacement of 3 distinct skin set-up markers was 3, 4, and 3 mm. Displacement of the scar wire in the X and Y direction was 0 and 1 mm, respectively. Among 28 verification scans performed, only 1 resulted in adaptive planning because of the initial presence of an air pocket in the lumpectomy cavity that resolved spontaneously during treatment.
  
  
  CONCLUSIONS
  APBI proton treatment using a supine approach was largely reproducible. Inter-fraction variation demonstrates 5-mm radial planning margins were adequate; however, outliers do occur and films should be reviewed critically and in real time. This technique is straightforward and could be used at any proton facility without the need for specialized equipment.
authors: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas. Electronic address: estrom@mdanderson.org.
authors: Eric A
authors: EA
authors: Strom
authors: Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas; Currently at Department of Radiotherapy Physics, University College London Hospitals NHS Foundation Trust, London, United Kingdom.
authors: Richard A
authors: RA
authors: Amos
authors: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors: Simona F
authors: SF
authors: Shaitelman
authors: Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors: Matthew D
authors: MD
authors: Kerr
authors: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors: Karen E
authors: KE
authors: Hoffman
authors: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors: Benjamin D
authors: BD
authors: Smith
authors: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors: Welela
authors: W
authors: Tereffe
authors: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors: Michael C
authors: MC
authors: Stauder
authors: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors: George H
authors: GH
authors: Perkins
authors: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors: Mayankumar D
authors: MD
authors: Amin
authors: Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors: Xiaochun
authors: X
authors: Wang
authors: Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors: Falk
authors: F
authors: Poenisch
authors: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors: Valentina
authors: V
authors: Ovalle
authors: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors: Thomas A
authors: TA
authors: Buchholz
authors: Department of Surgery, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors: Gildy
authors: G
authors: Babiera
authors: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors: Wendy A
authors: WA
authors: Woodward
mesh_terms: D001940:Breast / Q000502:physiology; D001943:Breast Neoplasms / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D056888:Patient Positioning / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D016683:Supine Position