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Cancer in NSW Aboriginal Peoples - Incidence, mortality and survival

It is essential to have accurate and complete collection and recording of health information on Aboriginal and Torres Strait Islander people if we are to make informed decisions about future service provision. Historically, health information about Aboriginal peoples, including cancer statistics, has been limited due to under-recording of Aboriginal status in administrative health data collections.

Over the past decade or so, a range of initiatives have been undertaken to improve the recording of Aboriginal status and much of this work has now flowed on to cancer statistics.

Mortality data from 1994 onwards is considered of sufficient quality to use as recorded by the NSW Central Cancer Registry (CCR). However, in order to analyse cancer incidence and survival, and minimise recording bias in NSW Aboriginal peoples, we used multiple imputation methods for cancer diagnosed from 1999 onwards (see the Methods section in Appendix 1 for more information). This has resulted in an extra 146 and 140 cancer cases in Aboriginal men and women respectively over 1999-2007.

After imputation for unstated Aboriginal status, Aboriginal peoples were found to have 7 per cent higher incidence of cancer than for NSW overall (9 per cent higher in men, 6 per cent higher in women), which was statistically significant. Specific cancers with significantly higher incidence rates in both Aboriginal men and women include head and neck, lung and bronchus, oesophagus and liver. Men also had significantly higher rates of cancer of the stomach, pancreas and unknown primary. Women had significantly higher rates of cervical cancer.

All-cancer mortality was also statistically significantly higher in Aboriginal peoples than for NSW overall, with excess cancer mortality estimated to be 69 per cent overall (68% in males, 73% in females). The differential between excess incidence and mortality indicates lower survival in Aboriginal peoples diagnosed with cancer. Significantly higher male and female Aboriginal cancer mortality was found for lung, head and neck, oesophagus, stomach, liver, pancreas, and kidney. Aboriginal men also had significantly higher mortality from bowel, prostate, and unknown primary. In Aboriginal women, excess mortality occurred from breast, cervical and uterine cancers. Outcomes for Aboriginal men with prostate cancer are particularly poor: despite significantly lower incidence of prostate cancer than NSW overall, Aboriginal men have 86 per cent higher mortality from prostate cancer.

Stage of disease at diagnosis is a major prognostic indicator for cancer outcomes, and differences in degree of spread (the modified CCR staging) at diagnosis between Aboriginal and non-Aboriginal people explain some of the differences in cancer mortality and survival. Overall, Aboriginal peoples have lower incidence rates of localised cancer; and in men this difference is significant. Correspondingly, they have higher rates of regional and distant cancers. Aboriginal peoples also have higher mortality across each degree of spread category - despite having lower incidence of localised cancer, they have higher mortality from localised cancer.

These mortality differentials are reflected in five-year cancer survival for Aboriginal peoples of 53 per cent, compared to 65 per cent for non-Aboriginal people. Five-year survival for Aboriginal men and women is 49 per cent and 57 per cent respectively, compared to 64 per cent and 67 per cent in non-Aboriginal men and women.