title: Contralateral breast dose after whole-breast irradiation: an analysis by treatment technique.
abstract: OBJECTIVE
  To investigate the contralateral breast dose (CBD) across a continuum of breast-conservation therapy techniques.
  
  
  METHODS
  An anthropomorphic phantom was CT-simulated, and six treatment plans were generated: open tangents, tangents with an external wedge on the lateral beam, tangents with lateral and medial external wedges, a simple segment plan (three segments per tangent), a complex segmental intensity-modulated radiotherapy (IMRT) plan (five segments per tangent), and a beamlet IMRT plan (>100 segments). For all techniques, the breast on the phantom was irradiated to 5000 cGy. Contralateral breast dose was measured at a uniform depth at the center and each quadrant using thermoluminescent detectors.
  
  
  RESULTS
  Contralateral breast dose varied with position and was 50 ± 7.3 cGy in the inner half, 24 ± 4.1 cGy at the center, and 16 ± 2.2 cGy in the outer half for the open tangential plan. Compared with an average dose of 31 cGy across all points for the open field, the average doses were simple segment 32 cGy (range, 99-105% compared with open technique), complex segment 34 cGy (range, 103-117% compared with open technique), beamlet IMRT 34 cGy (range, 103-124% compared with open technique), lateral wedge only 46 cGy (range, 133-175% compared with open technique), and medial and lateral wedge 96 cGy (range, 282-370% compared with open technique).
  
  
  CONCLUSIONS
  Single or dual wedge techniques resulted in the highest CBD increases compared with open tangents. To obtain the desired homogeneity to the treated breast while minimizing CBD, segmental and IMRT techniques should be encouraged over external physical compensators.
authors.affiliation: Department of Radiation Oncology, University of Michigan Health System, Ann Arbor, MI, USA.
authors.forename: Terence M
authors.initials: TM
authors.lastname: Williams
authors.forename: Jean M
authors.initials: JM
authors.lastname: Moran
authors.forename: Shu-Hui
authors.initials: SH
authors.lastname: Hsu
authors.forename: Robin
authors.initials: R
authors.lastname: Marsh
authors.forename: Beth
authors.initials: B
authors.lastname: Yanke
authors.forename: Benedick A
authors.initials: BA
authors.lastname: Fraass
authors.forename: Lori J
authors.initials: LJ
authors.lastname: Pierce
mesh_terms: D001940:Breast / Q000528:radiation effects*; D001943:Breast Neoplasms / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D019047:Phantoms, Imaging; D011874:Radiometry; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*