title: Hypofractionated whole-breast radiation therapy: does breast size matter?
abstract: OBJECTIVE
  To evaluate the effects of breast size on dose-volume histogram parameters and clinical toxicity in whole-breast hypofractionated radiation therapy using intensity modulated radiation therapy (IMRT).
  
  
  METHODS
  In this retrospective study, all patients undergoing breast-conserving therapy between 2005 and 2009 were screened, and qualifying consecutive patients were included in 1 of 2 cohorts: large-breasted patients (chest wall separation>25 cm or planning target volume [PTV]>1500 cm3) (n=97) and small-breasted patients (chest wall separation<25 cm and PTV<1500 cm3) (n=32). All patients were treated prone or supine with hypofractionated IMRT to the whole breast (42.4 Gy in 16 fractions) followed by a boost dose (9.6 Gy in 4 fractions). Dosimetric and clinical toxicity data were collected and analyzed using the R statistical package (version 2.12).
  
  
  RESULTS
  The mean PTV V95 (percentage of volume receiving>=95% of prescribed dose) was 90.18% and the mean V105 percentage of volume receiving>=105% of prescribed dose was 3.55% with no dose greater than 107%. PTV dose was independent of breast size, whereas heart dose and maximum point dose to skin correlated with increasing breast size. Lung dose was markedly decreased in prone compared with supine treatments. Radiation Therapy Oncology Group grade 0, 1, and 2 skin toxicities were noted acutely in 6%, 69%, and 25% of patients, respectively, and at later follow-up (>3 months) in 43%, 57%, and 0% of patients, respectively. Large breast size contributed to increased acute grade 2 toxicity (28% vs 12%, P=.008).
  
  
  CONCLUSIONS
  Adequate PTV coverage with acceptable hot spots and excellent sparing of organs at risk was achieved by use of IMRT regardless of treatment position and breast size. Although increasing breast size leads to increased heart dose and maximum skin dose, heart dose remained within our institutional constraints and the incidence of overall skin toxicity was comparable to that reported in the literature. Taken together, these data suggest that hypofractionated radiation therapy using IMRT is a viable and appropriate therapeutic modality in large-breasted patients.
authors.affiliation: Department of Radiation Oncology, The University of Texas Southwestern Medical Center, Dallas, Texas 75390-9183, USA. Raquibul.Hannan@gmail.com
authors.forename: Raquibul
authors.initials: R
authors.lastname: Hannan
authors.forename: Reid F
authors.initials: RF
authors.lastname: Thompson
authors.forename: Yu
authors.initials: Y
authors.lastname: Chen
authors.forename: Karen
authors.initials: K
authors.lastname: Bernstein
authors.forename: Rafi
authors.initials: R
authors.lastname: Kabarriti
authors.forename: William
authors.initials: W
authors.lastname: Skinner
authors.forename: Chin C
authors.initials: CC
authors.lastname: Chen
authors.forename: Evan
authors.initials: E
authors.lastname: Landau
authors.forename: Ekeni
authors.initials: E
authors.lastname: Miller
authors.forename: Marnee
authors.initials: M
authors.lastname: Spierer
authors.forename: Linda
authors.initials: L
authors.lastname: Hong
authors.forename: Shalom
authors.initials: S
authors.lastname: Kalnicki
mesh_terms: D001940:Breast / Q000033:anatomy & histology*; D001943:Breast Neoplasms / Q000473:pathology* / Q000532:radiotherapy*; D018270:Carcinoma, Ductal, Breast / Q000473:pathology / Q000532:radiotherapy; D002285:Carcinoma, Intraductal, Noninfiltrating / Q000473:pathology / Q000532:radiotherapy; D015331:Cohort Studies; D019583:Dose Fractionation, Radiation; D005260:Female; D006321:Heart / Q000528:radiation effects; D006801:Humans; D008168:Lung / Q000528:radiation effects; D008875:Middle Aged; D009929:Organ Size; D058958:Organs at Risk / Q000528:radiation effects; D056888:Patient Positioning / Q000379:methods; D016684:Prone Position; D011832:Radiation Injuries / Q000517:prevention & control; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects / Q000379:methods*; D012189:Retrospective Studies; D012867:Skin / Q000528:radiation effects; D016683:Supine Position; D047368:Tumor Burden