title: IORT with electrons as boost strategy during breast conserving therapy in limited stage breast cancer: long term results of an ISIORT pooled analysis.
abstract: OBJECTIVE
  Linac-based intraoperative radiotherapy with electrons (IOERT) was implemented to prevent local recurrences after breast conserving therapy (BCT) and was delivered as an intraoperative boost to the tumor bed prior to whole breast radiotherapy (WBI). A collaborative analysis has been performed by European ISIORT member institutions for long term evaluation of this strategy.
  
  
  METHODS
  Until 10/2005, 1109 unselected patients of any risk group have been identified among seven centers using identical methods, sequencing and dosage for intra- and postoperative radiotherapy. A median IOERT dose of 10 Gy was applied (90% reference isodose), preceding WBI with 50-54 Gy (single doses 1.7-2 Gy).
  
  
  RESULTS
  At a median follow up of 72.4 months (0.8-239), only 16 in-breast recurrences were observed, yielding a local tumor control rate of 99.2%. Relapses occurred 12.5-151 months after primary treatment. In multivariate analysis only grade 3 reached significance (p=0.031) to be predictive for local recurrence development. Taking into account patient age, annual in-breast recurrence rates amounted 0.64%, 0.34%, 0.21% and 0.16% in patients <40 years; 40-49 years; 50-59 years and ≥ 60 years, respectively.
  
  
  CONCLUSIONS
  In all risk subgroups, a 10 Gy IOERT boost prior to WBI provided outstanding local control rates, comparing favourably to all trials with similar length of follow up.
authors.affiliation: Department of Radiotherapy and Radio-Oncology, Paracelsus Medical University, Salzburg, Austria. Electronic address: g.fastner@salk.at.
authors.forename: Gerd
authors.initials: G
authors.lastname: Fastner
authors.forename: Felix
authors.initials: F
authors.lastname: Sedlmayer
authors.forename: Florian
authors.initials: F
authors.lastname: Merz
authors.forename: Heinrich
authors.initials: H
authors.lastname: Deutschmann
authors.forename: Roland
authors.initials: R
authors.lastname: Reitsamer
authors.forename: Christian
authors.initials: C
authors.lastname: Menzel
authors.forename: Christoph
authors.initials: C
authors.lastname: Stierle
authors.forename: Armando
authors.initials: A
authors.lastname: Farmini
authors.forename: Torsten
authors.initials: T
authors.lastname: Fischer
authors.forename: Antonella
authors.initials: A
authors.lastname: Ciabattoni
authors.forename: Alessandra
authors.initials: A
authors.lastname: Mirri
authors.forename: Eva
authors.initials: E
authors.lastname: Hager
authors.forename: Gabriele
authors.initials: G
authors.lastname: Reinartz
authors.forename: Claire
authors.initials: C
authors.lastname: Lemanski
authors.forename: Roberto
authors.initials: R
authors.lastname: Orecchia
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Valentini
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000704:Analysis of Variance; D001918:Brachytherapy / Q000379:methods*; D001943:Breast Neoplasms / Q000401:mortality* / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D015331:Cohort Studies; D018572:Disease-Free Survival; D004583:Electrons / Q000627:therapeutic use; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007430:Intraoperative Care / Q000379:methods*; D015412:Mastectomy, Segmental / Q000379:methods; D008875:Middle Aged; D015999:Multivariate Analysis; D009361:Neoplasm Invasiveness / Q000473:pathology; D009364:Neoplasm Recurrence, Local / Q000401:mortality / Q000517:prevention & control* / Q000628:therapy; D009367:Neoplasm Staging; D011182:Postoperative Care / Q000379:methods; D016016:Proportional Hazards Models; D011879:Radiotherapy Dosage; D018714:Radiotherapy, Adjuvant; D012189:Retrospective Studies; D018570:Risk Assessment; D016019:Survival Analysis; D013997:Time Factors; D016896:Treatment Outcome; D047368:Tumor Burden / Q000528:radiation effects
keywords: Boost; Breast cancer; Electrons; IOERT; Intraoperative radiotherapy