Abstract
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 Māori (Indigenous) and non-Māori New Zealanders with colon cancer, and the contribution of demographics, disease characteristics, patient comorbidity, treatment and healthcare factors to survival disparities was assessed.
Methods: Māori 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-Māori 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 Māori and 328 non-Māori patients with colon cancer were compared. Māori had a significantly poorer cancer survival than non-Māori (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 Māori 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 Māori and non-Māori 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 Māori compared with non-Māori New Zealanders with colon cancer.