title: Ethnic differences in breast cancer survival in New Zealand: contributions of differences in screening, treatment, tumor biology, demographics and comorbidities.
abstract: OBJECTIVE
  We investigated the breast cancer survival disparity between Indigenous Māori and non-Indigenous European women in New Zealand, and quantified the relative contributions of patient, tumor and healthcare system factors toward this disparity.
  
  
  METHODS
  All women diagnosed with breast cancer in Waikato, New Zealand, during 1999-2012 were identified from the Waikato Breast Cancer Register. Cancer-specific survivals were compared using Kaplan-Meier survival curves, while contributions of different factors toward the survival disparity were quantified with serial Cox proportional hazard modeling.
  
  
  RESULTS
  Of the 2,679 women included in this study, 2,260 (84.4%) were NZ European and 419 (15.6%) were Māori. Compared with NZ European women, Māori women had a significantly higher age-adjusted cancer-specific mortality (HR 2.02, 95% CI 1.59-2.58) with significantly lower 5-year (86.8 vs. 76.1%, p < 0.001) and 10-year (79.9 vs. 66.9%, p < 0.001%) crude cancer-specific survivals. Stage at diagnosis made the greatest contribution (approximately 25-40%), while screening, treatment and patient factors (i.e., comorbidity, obesity and smoking) contributed by approximately 15% each toward the survival disparity. The final model accounted for almost all of the cancer survival disparity (HR 1.07, 95% CI 0.80-1.44).
  
  
  CONCLUSIONS
  Māori women experience an age-adjusted risk of death from breast cancer, which is more than twice that for NZ European women. Equity-focussed improvements in health care, including increasing mammographic screening coverage and providing equitable quality and timely cancer care, may improve the survival disparity between Māori and NZ European women.
authors.affiliation: Waikato Clinical School, University of Auckland, Hamilton, New Zealand. Sanjeewa.Seneviratne@waikatodhb.health.nz.|Breast Cancer Research Office, Waikato Hospital, PO Box 934, Hamilton, 3240, New Zealand. Sanjeewa.Seneviratne@waikatodhb.health.nz.
authors.forename: Sanjeewa
authors.identifier: http://orcid.org/0000-0001-7148-4848
authors.initials: S
authors.lastname: Seneviratne
authors.affiliation: Waikato Clinical School, University of Auckland, Hamilton, New Zealand.
authors.forename: Ian
authors.initials: I
authors.lastname: Campbell
authors.affiliation: Māori Health Services, Waikato District Health Board, Hamilton, New Zealand.
authors.forename: Nina
authors.initials: N
authors.lastname: Scott
authors.affiliation: Waikato Breast Cancer Trust, Hamilton, New Zealand.
authors.forename: Rachel
authors.initials: R
authors.lastname: Shirley
authors.affiliation: Waikato Breast Cancer Trust, Hamilton, New Zealand.
authors.forename: Tamati
authors.initials: T
authors.lastname: Peni
authors.affiliation: Waikato Clinical School, University of Auckland, Hamilton, New Zealand.
authors.forename: Ross
authors.initials: R
authors.lastname: Lawrenson
mesh_terms: D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000175:diagnosis / Q000453:epidemiology* / Q000208:ethnology; D015897:Comorbidity; D055088:Early Detection of Cancer; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D008327:Mammography; D008875:Middle Aged; D009520:New Zealand; D012306:Risk; D044465:White People / Q000706:statistics & numerical data*
keywords: Breast cancer; Cancer survival; Ethnicity; Indigenous; Inequity