These researchers assessed trends in cancer survival inequalities in New Zealand by ethnic and income group, in a cohort of 126,477 people diagnosed with cancer between 1991 and 2004 and followed to 2006. The analysis measured inequalities pooled over time with excess mortality rate ratios (EMRRs) and changes over time in those inequalities by using EMRRs, excess mortality rate differences (EMRDs) and absolute differences in relative survival risks (RSRDs); all three were estimated by cancer-site and (for EMRRs only) pooled across all sites. Pooled over time and all sites, Māori had an EMRR of 1.29 (95% CI, 1.24 to 1.34) compared to non-Māori. The low- compared to high-income EMRR was 1.12 (95% CI, 1.09 to 1.15). 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 consistent across EMRRs, EMRDs and RSRDs. Ethnic inequalities in cancer survival persisted over time, with slower improvements for low-income people.
