title: Omission of radiotherapy after breast-conserving surgery: survival impact and time trends.
abstract: OBJECTIVE
  To evaluate the survival impact of omission of radiotherapy after breast-conserving surgery and the changes with time.
  
  
  METHODS
  Women aged 40-69 with non-metastasized T1-T2 breast cancer, who underwent breast-conserving surgery with axillary node dissection, with or without post-surgery radiotherapy, selected from the SEER (Surveillance, Epidemiology, and End Results) database. The analysis uses proportional hazards models.
  
  
  RESULTS
  Omission of radiotherapy as compared to delivery of radiotherapy was associated with an overall increased mortality hazard ratio of 1.346 (95% confidence interval: 1.204-1.504). Test of constancy showed significant changes with time. The time profile suggested an exponential-like increase from a baseline mortality hazard ratio of 1.17, or 17% excess of relative mortality risk, to a projected hazard ratio of 2.26, or more than doubling of relative mortality risk, for omission of radiotherapy.
  
  
  CONCLUSIONS
  Omission of radiotherapy in breast-conserving surgery is found to be independently associated with an increase in mortality. The data do not give support to omitting radiation or give rationale to clinical trials that would omit radiation.
authors.affiliation: Oncologisch Centrum, AZ-VUB, Free University Hospital of Brussels, 101 Laarbeeklaan, B-1090 Jette, Belgium.
authors.forename: Vincent
authors.initials: V
authors.lastname: Vinh-Hung
authors.forename: Mia
authors.initials: M
authors.lastname: Voordeckers
authors.forename: Jan
authors.initials: J
authors.lastname: Van de Steene
authors.forename: Guy
authors.initials: G
authors.lastname: Soete
authors.forename: Jan
authors.initials: J
authors.lastname: Lamote
authors.forename: Guy
authors.initials: G
authors.lastname: Storme
mesh_terms: D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000401:mortality* / Q000532:radiotherapy / Q000601:surgery*; D003131:Combined Modality Therapy; D015986:Confounding Factors, Epidemiologic; D005260:Female; D006801:Humans; D015412:Mastectomy, Segmental; D008875:Middle Aged; D016016:Proportional Hazards Models; D012044:Regression Analysis; D018426:SEER Program / Q000706:statistics & numerical data; D016019:Survival Analysis; D013997:Time Factors; D016896:Treatment Outcome