title: A population-based study of the fractionation of postlumpectomy breast radiation therapy.
abstract: OBJECTIVE
  The optimal fractionation schedule of post lumpectomy radiation therapy remains controversial. The objective of this study was to describe the fractionation of post-lumpectomy radiation therapy (RT) in Ontario, before and after the seminal Ontario Clinical Oncology Group (OCOG) trial, which showed the equivalence of 16- and 25-fraction schedules.
  
  
  METHODS
  This was a retrospective cohort study conducted by linking electronic treatment records to a population-based cancer registry. The study population included all patients who underwent lumpectomy for invasive breast cancer in Ontario, Canada, between 1984 and 2008.
  
  
  RESULTS
  Over the study period, 41,747 breast cancer patients received post lumpectomy radiation therapy to the breast only. Both 16- and 25-fraction schedules were commonly used throughout the study period. In the early 1980s, shorter fractionation schedules were used in >80% of cases. Between 1985 and 1995, the proportion of patients treated with shorter fractionation decreased to 48%. After completion of the OCOG trial, shorter fractionation schemes were once again widely adopted across Ontario, and are currently used in about 71% of cases; however, large intercenter variations in fractionation persisted.
  
  
  CONCLUSIONS
  The use of shorter schedules of post lumpectomy RT in Ontario increased after completion of the OCOG trial, but the trial had a less normative effect on practice than expected.
authors: Division of Cancer Care and Epidemiology, Queen's University Cancer Research Institute, Kingston, Ontario, Canada.
authors: Allison
authors: A
authors: Ashworth
authors: Weidong
authors: W
authors: Kong
authors: Timothy
authors: T
authors: Whelan
authors: William J
authors: WJ
authors: Mackillop
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000453:epidemiology / Q000532:radiotherapy* / Q000601:surgery; D019583:Dose Fractionation, Radiation; D005260:Female; D006297:Health Services Accessibility / Q000706:statistics & numerical data; D006801:Humans; D015412:Mastectomy, Segmental / Q000706:statistics & numerical data; D008498:Medical Record Linkage; D008875:Middle Aged; D009864:Ontario / Q000453:epidemiology; D011182:Postoperative Care / Q000706:statistics & numerical data; D018714:Radiotherapy, Adjuvant / Q000706:statistics & numerical data; D016032:Randomized Controlled Trials as Topic; D012042:Registries; D012044:Regression Analysis; D012189:Retrospective Studies