title: Early initiation of external beam radiotherapy (EBRT) may increase the risk of long-term toxicity in patients undergoing intraoperative radiotherapy (IORT) as a boost for breast cancer.
abstract: BACKGROUND
  Intraoperative radiotherapy (IORT) during breast-conserving surgery is increasingly used. We analyzed the influence of the interval between an IORT boost and external beam radiotherapy (EBRT) on late toxicity.
  
  
  METHODS
  Forty-eight patients received 20 Gy IORT (50 kV X-rays (Intrabeam, Carl Zeiss, Oberkochen, Germany) followed by 46-50 Gy EBRT with a median interval of 36 days (14-197). Late toxicity was assessed with the modified LENT SOMA score after a median of 36 months.
  
  
  RESULTS
  Twelve patients developed a higher grade fibrosis ( degrees II-III), three teleangiectases, one a breast edema grade degrees II, six retractions, four hyperpigmentations and five pain ( degrees II-III). The median interval between IORT and EBRT was significantly shorter in these patients (n=18) compared to the 30 patients without higher grade toxicity (29.5 days vs. 39.5 days, p=0.023, Mann-Whitney U-test).
  
  
  CONCLUSIONS
  Starting EBRT about 5-6 weeks after IORT appears to be associated with a decreased risk of chronic late toxicity compared with a shorter interval. The impact on local recurrence of prolonged gaps between IORT and EBRT is not known.
authors.affiliation: Department of Radiation Oncology, University of Heidelberg, University Medical Center Mannheim, Theodor-Kutzer Ufer 1-3, 68167 Mannheim, Germany. frederik.wenz@medma.uni-heidelberg.de
authors.forename: Frederik
authors.initials: F
authors.lastname: Wenz
authors.forename: Grit
authors.initials: G
authors.lastname: Welzel
authors.forename: Anke
authors.initials: A
authors.lastname: Keller
authors.forename: Elena
authors.initials: E
authors.lastname: Blank
authors.forename: Fatemeh
authors.initials: F
authors.lastname: Vorodi
authors.forename: Carsten
authors.initials: C
authors.lastname: Herskind
authors.forename: Oliver
authors.initials: O
authors.lastname: Tomé
authors.forename: Marc
authors.initials: M
authors.lastname: Sütterlin
authors.forename: Uta
authors.initials: U
authors.lastname: Kraus-Tiefenbacher
mesh_terms: D001943:Breast Neoplasms / Q000532:radiotherapy* / Q000601:surgery*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015412:Mastectomy, Segmental; D008875:Middle Aged; D011832:Radiation Injuries / Q000209:etiology*; D018714:Radiotherapy, Adjuvant / Q000009:adverse effects; D012307:Risk Factors; D013997:Time Factors