Aims.

Improvements in cancer survival may be distributed inequitably throughout populations and across time. We assess trends in ethnic and income cancer survival inequalities in New Zealand, overall and by site.

Methods

126,477 cancer patients diagnosed between 1991 and 2004, followed-up to 2006, were included. (i) Inequalities pooled over time were measured with excess mortality rate ratios (EMRRs). (ii) Interpretation of changes in inequalities over time can differ depending on whether one uses EMRRs, excess mortality rate differences (EMRD) or absolute differences in relative survival risks (RSRD); we estimated all three by cancer-site and (for EMRRs only) pooled across all sites.

Results

(i) Pooled over time and all sites, Māori had an EMRR of 1.29 (95% CI 1.24-1.34) compared to non-Māori. The low compared to high-income EMRR was 1.12 (1.08- 1.15). (ii) Pooled over cancers, there was no change in the ethnic EMRR over time but the income EMRR increased by 9% per decade (1-17%). Changes over time in site-specific inequalities were imprecisely measured, but the direction of change was usually but not always consistent across EMRRs, EMRDs and RSRDs.

Conclusions

There were persistent ethnic inequalities in cancer survival over time, and slower improvements for low-income people.