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Survival disparities in Indigenous and non-Indigenous New Zealanders with colon cancer: the role of patient comorbidity, treatment and health service factors
  1. Sarah Hill1,2,3,
  2. Diana Sarfati2,
  3. Tony Blakely2,
  4. Bridget Robson4,
  5. Gordon Purdie2,
  6. Jarvis Chen3,
  7. Elizabeth Dennett5,
  8. Donna Cormack4,
  9. Ruth Cunningham2,
  10. Kevin Dew2,6,
  11. Tim McCreanor7,
  12. Ichiro Kawachi3
  1. 1University of Edinburgh, Edinburgh, UK
  2. 2Department of Public Health, University of Otago, Wellington, New Zealand
  3. 3Department of Society, Human Development and Health, Harvard School of Public Health, Harvard University, Boston, Massachusetts, USA
  4. 4Te Rōpu Rangahau Hauora a Eru Pōmare, University of Otago, Wellington, New Zealand
  5. 5Department of Surgery, University of Otago, Wellington, New Zealand
  6. 6School of Social and Cultural Studies, Victoria University, Wellington, New Zealand
  7. 7Whaariki, Massey University, Auckland, New Zealand
  1. Correspondence to Dr Sarah Hill, Centre for International Public Health Policy, University of Edinburgh, Medical Quad, Teviot Place, Edinburgh EH8 9AG, UK; s.e.hill{at}


Background Ethnic disparities in cancer survival have been documented in many populations and cancer types. The causes of these inequalities are not well understood but may include disease and patient characteristics, treatment differences and health service factors. Survival was compared in a cohort of Maori (Indigenous) and non-Maori New Zealanders with colon cancer, and the contribution of demographics, disease characteristics, patient comorbidity, treatment and healthcare factors to survival disparities was assessed.

Methods Maori patients diagnosed as having colon cancer between 1996 and 2003 were identified from the New Zealand Cancer Registry and compared with a randomly selected sample of non-Maori patients. Clinical and outcome data were obtained from medical records, pathology reports and the national mortality database. Cancer-specific survival was examined using Kaplan–Meier survival curves and Cox hazards modelling with multivariable adjustment.

Results 301 Maori and 328 non-Maori patients with colon cancer were compared. Maori had a significantly poorer cancer survival than non-Maori (hazard ratio (HR)=1.33, 95% CI 1.03 to 1.71) that was not explained by demographic or disease characteristics. The most important factors contributing to poorer survival in Maori were patient comorbidity and markers of healthcare access, each of which accounted for around a third of the survival disparity. The final model accounted for almost all the survival disparity between Maori and non-Maori patients (HR=1.07, 95% CI 0.77 to 1.47).

Conclusion Higher patient comorbidity and poorer access and quality of cancer care are both important explanations for worse survival in Maori compared with non-Maori New Zealanders with colon cancer.

  • colonic neoplasms
  • delivery of healthcare
  • ethnic groups
  • New Zealand
  • survival analysis

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  • Funding This work was supported by the Cancer Society of New Zealand (grant no 05/16) and by Fulbright New Zealand which provided scholarship support to SH.

  • Competing interests None.

  • Ethics approval Ethics approval was provided by New Zealand Multi-Region Ethics Committee (Ref: MEC/05/06/069).

  • Provenance and peer review Not commissioned; externally peer reviewed.