title: A population-based study of factors affecting the use of radiotherapy for endometrial cancer.
abstract: OBJECTIVE
  To describe the use of adjuvant radiotherapy for endometrial cancer in Ontario, and identify factors associated with its use, and to determine whether variation in the use of radiation is associated with differences in survival.
  
  
  METHODS
  This was a retrospective, population-based, cohort study of all patients who had a hysterectomy for endometrial cancer in Ontario between 1992 and 2003. We used multiple logistic regression to identify health system-related factors associated with the use of radiotherapy, while controlling for disease- and patient-related factors. Survival and cancer cause-specific survival were compared among regions of the province with higher and lower rates of use of radiotherapy.
  
  
  RESULTS
  The study population included a total of 9411 women with a median age of 63 years. Overall, 26.2% received adjuvant radiotherapy. Patients living further from regional cancer centres were slightly less likely to receive radiation (P = 0.02). Patients who had their surgery during longer prevailing waiting times for radiotherapy were less likely to receive radiation (P = 0.04). The use of radiotherapy varied widely from 18.0 to 34.3% among the catchment areas of provincial radiotherapy centres (P < 0.0001). In the overall population, there was no difference in survival among regions with higher and lower rates of use of radiotherapy. However, in the subgroup of cases with clear cell and serous carcinomas, both overall survival and cancer cause-specific survival were significantly lower in regions with lower rates of use of radiotherapy (P < 0.05). This difference remained significant after controlling for other factors (P < 0.05; hazard ratio 1.43; 95% confidence limits 1.06-1.93).
  
  
  CONCLUSIONS
  Health system-related factors unrelated to patients' needs affect the use of adjuvant radiotherapy in Ontario. Lower rates of use of adjuvant radiotherapy are associated with lower rates of survival in patients with serous and clear cell carcinomas.
authors.affiliation: Division of Cancer Care and Epidemiology, Queen's University Cancer Research Institute, Kingston, Ontario, Canada.
authors.forename: T P
authors.initials: TP
authors.lastname: Hanna
authors.forename: H
authors.initials: H
authors.lastname: Richardson
authors.forename: Y
authors.initials: Y
authors.lastname: Peng
authors.forename: W
authors.initials: W
authors.lastname: Kong
authors.forename: J
authors.initials: J
authors.lastname: Zhang-Salomons
authors.forename: W J
authors.initials: WJ
authors.lastname: Mackillop
mesh_terms: D000368:Aged; D015331:Cohort Studies; D016889:Endometrial Neoplasms / Q000188:drug therapy / Q000532:radiotherapy* / Q000601:surgery; D005260:Female; D006801:Humans; D007044:Hysterectomy / Q000379:methods; D008875:Middle Aged; D009864:Ontario; D010818:Practice Patterns, Physicians'; D018714:Radiotherapy, Adjuvant / Q000706:statistics & numerical data*; D012189:Retrospective Studies; D015996:Survival Rate