title: Accelerated partial-breast irradiation using intensity-modulated proton radiotherapy: do uncertainties outweigh potential benefits?
abstract: OBJECTIVE
  Passive scattering proton beam (PSPB) radiotherapy for accelerated partial-breast irradiation (APBI) provides superior dosimetry for APBI three-dimensional conformal photon radiotherapy (3DCRT). Here we examine the potential incremental benefit of intensity-modulated proton radiotherapy (IMPT) for APBI and compare its dosimetry with PSPB and 3DCRT.
  
  
  METHODS
  Two theoretical IMPT plans, TANGENT_PAIR and TANGENT_ENFACE, were created for 11 patients previously treated with 3DCRT APBI and were compared with PSPB and 3DCRT plans for the same CT data sets. The impact of range, motion and set-up uncertainties as well as scanned spot mismatching between fields of IMPT plans was evaluated.
  
  
  RESULTS
  IMPT plans for APBI were significantly better regarding breast skin sparing (p<0.005) and other normal tissue sparing than 3DCRT plans (p<0.01) with comparable target coverage (p=ns). IMPT plans were statistically better than PSPB plans regarding breast skin (p<0.002) and non-target breast (p<0.007) in higher dose regions but worse or comparable in lower dose regions. IMPT plans using TANGENT_ENFACE were superior to that using TANGENT_PAIR in terms of target coverage (p<0.003) and normal tissue sparing (p<0.05) in low-dose regions. IMPT uncertainties were demonstrated for multiple causes. Qualitative comparison of dose-volume histogram confidence intervals for IMPT suggests that numeric gains may be offset by IMPT uncertainties.
  
  
  CONCLUSIONS
  Using current clinical dosimetry, PSPB provides excellent dosimetry compared with 3DCRT with fewer uncertainties compared with IMPT.
  
  
  CONCLUSIONS
  As currently delivered in the clinic, PSPB planning for APBI provides as good or better dosimetry than IMPT with less uncertainty.
authors.affiliation: Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
authors.forename: X
authors.initials: X
authors.lastname: Wang
authors.forename: X
authors.initials: X
authors.lastname: Zhang
authors.forename: X
authors.initials: X
authors.lastname: Li
authors.forename: R A
authors.initials: RA
authors.lastname: Amos
authors.forename: S F
authors.initials: SF
authors.lastname: Shaitelman
authors.forename: K
authors.initials: K
authors.lastname: Hoffman
authors.forename: R
authors.initials: R
authors.lastname: Howell
authors.forename: M
authors.initials: M
authors.lastname: Salehpour
authors.forename: S X
authors.initials: SX
authors.lastname: Zhang
authors.forename: T L
authors.initials: TL
authors.lastname: Sun
authors.forename: B
authors.initials: B
authors.lastname: Smith
authors.forename: W
authors.initials: W
authors.lastname: Tereffe
authors.forename: G H
authors.initials: GH
authors.lastname: Perkins
authors.forename: T A
authors.initials: TA
authors.lastname: Buchholz
authors.forename: E A
authors.initials: EA
authors.lastname: Strom
authors.forename: W A
authors.initials: WA
authors.lastname: Woodward
mesh_terms: D001943:Breast Neoplasms / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D017785:Photons / Q000627:therapeutic use; D061766:Proton Therapy; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D020266:Radiotherapy, Conformal / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated; D011522:Protons
chemical_list: D011522:Protons