title: Impact of radiotherapy on background parenchymal enhancement in breast magnetic resonance imaging.
abstract: BACKGROUND
  While many studies have shown that hormones can influence background parenchymal enhancement (BPE) in breast magnetic resonance imaging (MRI), only few have directly address the effect of radiotherapy. The purpose of this study was to evaluate the impact of radiotherapy on BPE in breast MRI.
  
  
  METHODS
  A retrospective search identified 62 women with unilateral breast cancer who had a breast MRI both before and after radiotherapy following breast-conserving surgery. In our study, we assumed that systemic therapy affected both breasts equivalently. We rated the level of BPE of both breasts using a four- point categorical scale. A change in the level of BPE prior to and after treatment was compared in the diseased and contralateral breasts.
  
  
  RESULTS
  All patients received a 4256 to 6480 cGy dose of whole breast radiotherapy over 3-7 weeks. The mean timing of the follow-up study was 6.6 months after completion of radiotherapy. Although the BPE showed a decrease in both breasts after treatment, there was a significant reduction of BPE in the irradiated breast compared with the contralateral breast (1.18 versus 0.98 average reduction in BPE level, p=0.042).
  
  
  CONCLUSIONS
  Radiotherapy is associated with decrease in BPE with MRI.
authors.affiliation: Department of Radiology, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Korea E-mail : rad-ksh@catholic.ac.kr.
authors.forename: Yun Ju
authors.initials: YJ
authors.lastname: Kim
authors.forename: Sung Hun
authors.initials: SH
authors.lastname: Kim
authors.forename: Byung Gil
authors.initials: BG
authors.lastname: Choi
authors.forename: Bong Joo
authors.initials: BJ
authors.lastname: Kang
authors.forename: Hyeon Sook
authors.initials: HS
authors.lastname: Kim
authors.forename: Eun Suk
authors.initials: ES
authors.lastname: Cha
authors.forename: Byung Joo
authors.initials: BJ
authors.lastname: Song
mesh_terms: D001940:Breast / Q000473:pathology*; D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy* / Q000601:surgery; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000009:adverse effects*; D008327:Mammography / Q000009:adverse effects; D015412:Mastectomy, Segmental; D012189:Retrospective Studies