Good evidence exists as to large and increasing ethnic and Indigenous inequalities worldwide in cancer incidence and mortality. Much of this inequality is considered to be preventable through the control of tobacco, obesity, alcohol and infectious diseases. Moreover, further gains are likely with policies addressing equal access and quality of health care. These researchers sought to determine how cancer contributes to overall ethnic gaps in all-cause mortality over time in the New Zealand population. They also examined how individual cancers contribute to the overall ethnic gaps in cancer mortality, and aimed to estimate how changes in cancer incidence contributes to trends in ethnic inequalities in mortality. New Zealand mortality and Cancer Registry data from 1981, 1986, 1991, 1996, 2001 and 2006 were probabilistically linked to 3 to 5 subsequent years of mortality (68 million person-years) and cancer registrations (87 million person-years), then weighted for linkage bias. Age-standardised rate differences (SRDs) for Māori (Indigenous) and Pacific peoples, each compared to European/Other, were decomposed by cancer type. The contribution of cancer to all-cause mortality inequalities increased (both in absolute and percentage terms) from 1981–86 to 2006–11 in Māori males (SRD 72.5 to 102.0 per 100,000) and females (SRD 72.2 to 109.4), and Pacific females (SRD −9.8 to 42.2) each compared to European/Other. Excess mortality (SRDs) increased for breast cancer in Māori females (linear trend p<0.01) and prostate (p<0.01) and colorectal cancers (p<0.01) in Māori males. Cancers contributing to the incidence gap were generally similar to the cancers contributing to excess mortality. Breast cancer incidence increased in all ethnic groups but at a faster rate in Māori and Pacific females thus widening the incidence gap (SRD linear trend for both was p<0.01). The incidence gap (SRDs) also increased for endometrial (Pacific females p<0.01) and liver cancers (Māori males p=0.04), while the gap decreased for cervical cancer (Māori females p=0.03). Incidence of colorectal cancer increased among Māori males and females to levels similar to European/Other, thus significantly narrowing the ethnic difference that previously favoured Māori (p<0.01). In the 2006–11 cohort, lung, breast and stomach cancers made the largest contribution to absolute inequalities (SRDs) in mortality among Māori and Pacific peoples, and the largest contributors to the ethnic gap in cancer incidence were lung, breast, stomach, endometrial and liver cancer.
