Survival disparities in Indigenous and non-Indigenous New Zealanders with colon cancer: the role of patient comorbidity, treatment and health service factors.
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).


CONCLUSIONS
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.
Hill
Sarah
S
University of Edinburgh, Edinburgh EH8 9AG, UK. s.e.hill@ed.ac.uk
Sarfati
Diana
D
Blakely
Tony
T
Robson
Bridget
B
Purdie
Gordon
G
Chen
Jarvis
J
Dennett
Elizabeth
E
Cormack
Donna
D
Cunningham
Ruth
R
Dew
Kevin
K
McCreanor
Tim
T
Kawachi
Ichiro
I
D003110:Colonic Neoplasms / Q000150:complications / Q000208:ethnology* / Q000628:therapy; D015897:Comorbidity; D006297:Health Services Accessibility; D054624:Health Status Disparities; D054625:Healthcare Disparities / Q000208:ethnology*; D006801:Humans; D053208:Kaplan-Meier Estimate; D009520:New Zealand / Q000453:epidemiology; D044382:Population Groups; D016016:Proportional Hazards Models