ArticlesCancer diagnosis, treatment, and survival in Indigenous and non-Indigenous Australians: a matched cohort study
Introduction
The Aboriginal and Torres Strait Islander population of Australia (referred to in this article as Indigenous) account for 2·4% of the total population.1 Like other such groups, their history has been a powerful determinant of socioeconomic status.2 Since colonisation, Indigenous Australians have lost some of their cultural expression and practices.3 This disempowerment manifests in their poor education and low levels of employment. They are on average younger, live more remotely, and have poorer health than other Australians. Their life expectancy at birth is also 20 years shorter, with much of the excess mortality attributable to heart disease, injury, diabetes, chronic renal failure, smoking-related lung disease, and suicide.1
This disparity also exists for cancer. In Australia, the reported incidence of cancer in Indigenous people is lower than or equivalent to that in the general population,1, 4 but the mortality rate is higher.5 Indigenous Australians have a high incidence of rapidly fatal cancers such as cancers of the lung and liver, and a very low incidence of cancers with better survival, particularly melanoma (one of the most common cancers in white Australians).6 However, studies that have allowed for differences in cancer types and stage at diagnosis showed that case-fatality rates in Indigenous Australians with cancer were twice that of their non-Indigenous counterparts.7, 8 Little is known about why this should be so, although possible reasons include less access to high-quality treatment and a higher prevalence of comorbidities that might limit treatment options—such as diabetes, acute coronary conditions, and chronic renal failure.
In a study done in the Northern Territory of Australia,9 stage-adjusted survival rates were lower for Indigenous people than for non-Indigenous people with cancers of the colon and rectum, breast, cervix, and for non-Hodgkin lymphoma. Cancer survival was also strongly associated with a patient's first language. For Indigenous people whose first language was English, lower cancer survival was entirely explained by more advanced cancer at diagnosis; for those whose first language was an Indigenous language, incomplete treatment and other unidentified factors were also associated with lower cancer survival.
The difficulty in comparing health outcomes of Indigenous and non-Indigenous people is that these groups are so highly disparate that it is not easy to distinguish the factors that cause the health differential. We therefore decided to investigate this issue in relation to cancer survival with a new approach. By matching Indigenous and non-Indigenous cancer patients to create groups with similar age distributions and types of cancer, and living in similar regions, we could explore the roles of stage at diagnosis, treatment uptake, and comorbidities in the survival rates of these two populations. In view of the matched design, we postulated that equal access to public-health services in Queensland would result in similar cancer survival rates in the Indigenous and non-Indigenous cancer patients studied.
Section snippets
Participants
The study was done in Queensland, the north-eastern state of Australia, which constitutes 23% of the continental land mass and has a population of 3·9 million, around 126 000 of whom identify themselves as Indigenous (28% of the total Indigenous population of Australia). All Indigenous people residing in Queensland and diagnosed with cancer between 1997 and 2002 were identified through Queensland public hospitals or the Queensland Cancer Registry, and were eligible for inclusion. Indigenous
Results
We identified 824 eligible Indigenous cancer patients and an equal number of eligible non-Indigenous patients. Information from medical charts was available for 815 Indigenous people (610 Aboriginal patients, 158 Torres Strait Islanders, and 47 who identified themselves as both Aboriginal and Torres Strait Islander). Overall, 4% of Indigenous cases were children (0–14 years), 11% were aged 15–39 years, 40% aged 40–59 years, and the remaining 45% were 60 years or older. For Indigenous people in
Discussion
Compared with non-Indigenous Australian cancer patients, Indigenous patients of a similar age, sex, place of residence, type of cancer, and public-health care in Queensland, fared worse. The likelihood of death from cancer was about 30% higher for Indigenous than for non-Indigenous cases, after taking into account cancer stage at diagnosis, cancer treatment, and higher rates of comorbidities in Indigenous individuals.
In Australia, as in most other countries, ethnicity (as recorded in
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