title: Stage at diagnosis and comorbidity influence breast cancer survival in First Nations women in Ontario, Canada.
abstract: BACKGROUND
  Indigenous populations in Canada and abroad have poorer survival after a breast cancer diagnosis compared with their geographic counterparts; however, the influence of many demographic, personal, tumor, and treatment factors has not been examined to describe this disparity according to stage at diagnosis.
  
  
  METHODS
  A case-case design was employed to compare First Nations (FN) women (n = 287) to a frequency-matched random sample of non-FN women (n = 671) diagnosed with breast cancer within the Ontario Cancer Registry. Women were matched on period of diagnosis (1995-1999 and 2000-2004), age at diagnosis (<50 vs. ≥50), and Regional Cancer Centre (RCC). Stage and other factors were collected from medical charts at the RCCs. Survival was compared using an adjusted Cox proportional hazards model and stratified by stage at diagnosis (I, II, and III-IV). Determinants of survival in FN women stratified by stage at diagnosis were also modeled.
  
  
  RESULTS
  Survival was more than three times poorer for FN women diagnosed at stage I than for non-FN women (HR = 3.10, 95% CI = 1.39-6.88). The risk of death after a stage I breast cancer diagnosis was about five times higher among FN women with a comorbidity other than diabetes (HR = 4.65, 95% CI = 1.39-15.53) and was more than five times greater for women with diabetes (HR = 5.49, 95% CI = 1.69-17.90) than for those without a comorbidity.
  
  
  CONCLUSIONS
  Having a preexisting comorbidity was the most important factor in explaining the observed survival disparity among FN women.
  
  
  CONCLUSIONS
  Improving the general health status of FN women could increase their survival after an early-stage breast cancer diagnosis.
authors.affiliation: Prevention and Cancer Control, Cancer Care Ontario, Toronto, Ontario, Canada.
authors.forename: Amanda J
authors.initials: AJ
authors.lastname: Sheppard
authors.forename: Anna M
authors.initials: AM
authors.lastname: Chiarelli
authors.forename: Loraine D
authors.initials: LD
authors.lastname: Marrett
authors.forename: E Diane
authors.initials: ED
authors.lastname: Nishri
authors.forename: Maureen E
authors.initials: ME
authors.lastname: Trudeau
mesh_terms: D000293:Adolescent; D000328:Adult; D001943:Breast Neoplasms / Q000175:diagnosis* / Q000453:epidemiology* / Q000401:mortality*; D002170:Canada / Q000453:epidemiology; D015897:Comorbidity; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D009367:Neoplasm Staging; D011379:Prognosis; D012307:Risk Factors; D015996:Survival Rate; D055815:Young Adult