title: Whole breast irradiation for small-sized breasts after conserving surgery: is the field-in-field technique optimal?
abstract: BACKGROUND
  To determine the optimal whole breast irradiation technique in patients with small-sized breasts, tangential and field-in-field IMRT (FIF) techniques were compared.
  
  
  METHODS
  Sixteen patients with ≤3 cm breast height and ≤350 cc volume were included. Seven patients had 4D CTs performed. The planning target volumes (PTV), editing 5 and 2 mm from the surface on the whole breast, were delineated and called PTV(5) and PTV(2), respectively. Dose-volume histograms of tangential techniques with open beam (OT) and wedge filter (WT), conventional FIF (cFIF), and modified FIF (mFIF) blocking out the lung were produced. Various dose-volume parameters, the dose heterogeneity index (DHtrI), dose homogeneity index (DHmI), and PTV dose improvement (PDI) were calculated.
  
  
  RESULTS
  OT compared with WT showed a significantly favorable V 90 of the heart and lung, and PTV(5)-dose distribution. Comparing OT and cFIF, OT showed significant improvement in the V 95 of PTV(2), whereas cFIF showed significant improvement in the V 95, DHtrI, DHmI, and PDI of the PTV(5). In comparing cFIF and mFIF, mFIF showed improved dose distributions of the heart and lung, while cFIF presented the better V 95, DHtrI, DHmI, and PDI of the PTV(5). Respiratory influences on the absolute dose were mostly within 1 %. The ratio of free breathing and each respiratory phase was similar among OT, cFIF, and mFIF.
  
  
  CONCLUSIONS
  cFIF has favorable dose conformity and is suggested to be an optimal method for small-sized breasts. However, OT for dose coverage close to the skin and mFIF for normal tissue may also be potential alternatives. Respiratory effects are minimal.
authors.affiliation: Department of Radiation Oncology, Guro Hospital, Korea University Medical Center, Gurodong-gil 97, Guro-gu, Seoul, 152-703, Republic of Korea.
authors.forename: Dae Sik
authors.initials: DS
authors.lastname: Yang
authors.forename: Jung Ae
authors.initials: JA
authors.lastname: Lee
authors.forename: Won Sup
authors.initials: WS
authors.lastname: Yoon
authors.forename: Se Young
authors.initials: SY
authors.lastname: Chung
authors.forename: Suk
authors.initials: S
authors.lastname: Lee
authors.forename: Chul Yong
authors.initials: CY
authors.lastname: Kim
authors.forename: Young Je
authors.initials: YJ
authors.lastname: Park
authors.forename: Gil Soo
authors.initials: GS
authors.lastname: Son
mesh_terms: D000328:Adult; D001943:Breast Neoplasms / Q000532:radiotherapy* / Q000601:surgery; D005260:Female; D006801:Humans; D015412:Mastectomy, Segmental; D008875:Middle Aged; D011829:Radiation Dosage