title: The impact of treatment interruptions on locoregional control during postoperative breast irradiation.
abstract: OBJECTIVE
  Patients treated in the years 1990-2003 with breast conserving surgery and postoperative adjuvant radiotherapy were retrospectively analyzed in order to determine the impact of radiotherapy interruptions on the treatment outcome.
  
  
  METHODS
  470 patients received breast irradiation with (60)Co or with 4MV photon linear accelerator (total dose 50 Gy, range 46-54). Four hundred and sixty-two (98%) patients had boost dose of 10-20 Gy to the tumor bed either with photon or electron irradiation. Irradiation of the lymphatic fields was carried out according to the number of involved nodes. Even one day of treatment break was accepted as treatment interruption. Unplanned treatment interruptions occurred in 423 (90%) patients. A total of 196 (41%) patients had no treatment breaks or had interruptions of 7 days or less and 274 (59%) patients had treatment interruptions longer than 7 days. Locoregional control (LC) and overall survival (OS) rates were estimated by Kaplan-Meier method. The groups were compared with log-rank x(2) and Pearson x(2) tests.
  
  
  RESULTS
  For all patients 5-year LC and OS rates were 91% and 85%, and 10-year rates were 86% and 75%, respectively. LC rates for the group of patients without interruptions or with an interruption of less than a week were 95% for 5 years and 90% for 10 years. Five- and 10-year LC rates for the patients with interruptions of 8 days or more were 87% and 83%, respectively (p=0.02).
  
  
  CONCLUSIONS
  This retrospective study shows that postoperative irradiation interruptions of more than a week negatively impact LC.
authors.affiliation: Department of Radiation Oncology, Istanbul University, Cerrahpasa Medical School, Istanbul, Turkey. nuranbese@superonline.com
authors.forename: N S
authors.initials: NS
authors.lastname: Bese
authors.forename: P A
authors.initials: PA
authors.lastname: Sut
authors.forename: N
authors.initials: N
authors.lastname: Sut
authors.forename: A
authors.initials: A
authors.lastname: Ober
mesh_terms: D000328:Adult; D001943:Breast Neoplasms / Q000532:radiotherapy* / Q000601:surgery; D003131:Combined Modality Therapy; D005260:Female; D006801:Humans; D015412:Mastectomy, Segmental; D009364:Neoplasm Recurrence, Local / Q000453:epidemiology*; D011184:Postoperative Period; D012189:Retrospective Studies; D017211:Treatment Failure; D016896:Treatment Outcome