title: Concomitant intensity modulated boost during whole breast hypofractionated radiotherapy--a feasibility and toxicity study.
abstract: BACKGROUND
  Breast cancer sensitivity to large fraction size may be enhanced using hypofractionated concomitant boost radiotherapy (CBRT), thereby shortening overall treatment time. This ethics approved, prospective single cohort feasibility study was designed to evaluate the dosimetry and toxicity of CBRT using an intensity-modulated radiotherapy (IMRT) technique, compared with a standard sequential boost technique (SBT).
  
  
  METHODS
  Fifteen women (11 right-sided; 4 left-sided) received 42.4 Gy to the whole breast and an additional 10.08 Gy to the tumor bed in 16 daily fractions, using IMRT and standard dose constraints. Each patient was replanned with the SBT, using mixed photon-electrons. Clinical target volume (CTV), dose evaluation volume (DEV), and organs at risk (OAR) dose distributions were compared with the SBT. Toxicity and treatment times were prospectively recorded.
  
  
  RESULTS
  All 15 CBRT plans achieved the desired CTV (V(49.9Gy) ≥ 99%) and DEV (V(49.9Gy) ≥ 95%), coverage of the boost, compared with only 10 (66.7%, p=0.03), and 12 (80%, p=0.125) SBT plans, respectively. Ipsilateral lung (p<0.0001), and heart (right-sided, p=0.001; left-sided, p=0.13) doses were lower. Grade 3 acute toxicity occurred in 1 (6.7%) patient. At 1 year, two (13.3%) additional patients had overall grade 2 late toxicity, compared with baseline. No grade 3-4 late toxicity was observed.
  
  
  CONCLUSIONS
  CBRT using IMRT improved boost coverage and lowered OAR doses, compared with SBT. Toxicities were acceptable using a daily boost of 3.28 Gy. While resource utilization was greater, overall treatment time was reduced.
authors: Radiation Medicine Program, Princess Margaret Hospital, University Health Network, Toronto, Ontario, Canada.
authors: Amy Yuen Meei
authors: AY
authors: Teh
authors: Lorraine
authors: L
authors: Walsh
authors: Thomas G
authors: TG
authors: Purdie
authors: Allen
authors: A
authors: Mosseri
authors: Wei
authors: W
authors: Xu
authors: Wilfred
authors: W
authors: Levin
authors: C Anne
authors: CA
authors: Koch
authors: Anthony
authors: A
authors: Fyles
authors: Fei-Fei
authors: FF
authors: Liu
authors: B C John
authors: BC
authors: Cho
mesh_terms: D001943:Breast Neoplasms / Q000532:radiotherapy* / Q000601:surgery; D019583:Dose Fractionation, Radiation; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008875:Middle Aged; D011446:Prospective Studies; D011879:Radiotherapy Dosage; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects / Q000379:methods*; D018709:Statistics, Nonparametric; D016896:Treatment Outcome