title: Comparison of modulated electron radiotherapy to conventional electron boost irradiation and volumetric modulated photon arc therapy for treatment of tumour bed boost in breast cancer.
abstract: OBJECTIVE
  To compare few leaf electron collimator (FLEC)-based modulated electron radiotherapy (MERT) to conventional direct electron (DE) and volumetric modulated photon arc therapy (VMAT) for the treatment of tumour bed boost in breast cancer.
  
  
  METHODS
  Fourteen patients with breast cancer treated by lumpectomy and requiring post-operative whole breast radiotherapy with tumour bed boost were planned retrospectively using conventional DE, VMAT and FLEC-based MERT. The planning goal was to deliver 10Gy to at least 95% of the tumour bed volume. Dosimetry parameters for all techniques were compared.
  
  
  RESULTS
  Dose evaluation volume (DEV) coverage and homogeneity were best for MERT (D(98)=9.77Gy, D(2)=11.03Gy) followed by VMAT (D(98)=9.56Gy, D(2)=11.07Gy) and DE (D(98)=9.81Gy, D(2)=11.52Gy). Relative to the DE plans, the MERT plans predicted a reduction of 35% in mean breast dose (p<0.05), 54% in mean lung dose (p<0.05) and 46% in mean body dose (p<0.05). Relative to the VMAT plans, the MERT plans predicted a reduction of 24%, 36% and 39% in mean breast dose, heart dose and body dose, respectively (p<0.05).
  
  
  CONCLUSIONS
  MERT plans were a considerable improvement in dosimetry over DE boost plans. There was a dosimetric advantage in using MERT over VMAT for increased DEV conformity and low-dose sparing of healthy tissue including the integral dose; however, the cost is often an increase in the ipsilateral lung high-dose volume.
authors: Medical Physics Unit, McGill University, Montreal, Quebec, Canada. andrew.alexander@mail.mcgill.ca
authors: Andrew
authors: A
authors: Alexander
authors: Emilie
authors: E
authors: Soisson
authors: Tarek
authors: T
authors: Hijal
authors: Arman
authors: A
authors: Sarfehnia
authors: Jan
authors: J
authors: Seuntjens
mesh_terms: D001943:Breast Neoplasms / Q000532:radiotherapy*; D004583:Electrons / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D017785:Photons / Q000627:therapeutic use*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D012189:Retrospective Studies