A comparative study of cancer incidence, diagnosis, treatment and survival between Indigenous and non-Indigenous people in Queensland

Suzanne Moore (2010). A comparative study of cancer incidence, diagnosis, treatment and survival between Indigenous and non-Indigenous people in Queensland PhD Thesis, School of Population Health, The University of Queensland.

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Author Suzanne Moore
Thesis Title A comparative study of cancer incidence, diagnosis, treatment and survival between Indigenous and non-Indigenous people in Queensland
School, Centre or Institute School of Population Health
Institution The University of Queensland
Publication date 2010-07
Thesis type PhD Thesis
Supervisor Professor Adele Green
Dr Patricia Valery
Ms Gail Garvey
Professor Michael Coory
Total pages 276
Total colour pages 31
Total black and white pages 245
Subjects 11 Medical and Health Sciences
Abstract/Summary Abstract Context: The burden of cancer for Indigenous people in general has not been comprehensively explored, despite increasing evidence that Indigenous people have significantly greater morbidity and mortality due to the disease than other Australians. This population-based study broadly examines for the first time, the management and outcome of cancer for Indigenous people in Queensland, Australia. Objective: To compare cancer incidence and mortality rates for Indigenous people with those for the whole state of Queensland (Phase One) and then compare and contrast clinical features, cancer treatment and survival of Indigenous people with cancer to a matched cohort of non-Indigenous people with cancer, also diagnosed or treated in the Queensland public health system (Phase Two). Setting and design: Phase One used data for the period 1997 to 2006, ascertained from the population-based Queensland Cancer Registry, to calculate cancer incidence and mortality rates among Indigenous people and the whole Queensland population. Phase Two was a population-based study comparing Indigenous cancer cases diagnosed between 1998 and 2004, to a random sample of non-Indigenous people diagnosed with the same incident cancers, matched for age, sex and degree of rurality. For comparability, only those diagnosed or receiving treatment in a Queensland public health facility were included. Methods: Phase One: Age-standardised rates of cancer incidence and mortality were calculated using both the total 2001 Australian population and the World Standard Population as the standard populations. Phase Two: Clinical data pertaining to cancer stage, prevalence of comorbidities, treatment and time to treatment were collected from Queensland Health records. Descriptive analyses examined differences between Indigenous and non-Indigenous people for all cancers combined and for three individual cancer groups, namely lung, head and neck, and breast. Chi-squared analysis and Fishers Exact test were used for comparisons of categorical data (proportions), t-tests for normally-distributed data (means), and non-parametric tests (Kruskal-Wallis) for non-normally-distributed data (medians). Logistic regression was used to assess crude and adjusted proportional differences, and Cox regression for crude and adjusted survival analyses, accounting for stage of cancer at diagnosis, the presence of comorbidities, socioeconomic status, and cancer treatment. Results: Phase One: A total of 1936 incident cancer cases occurred among the Indigenous population of Queensland in the period 1997 to 2006, corresponding to an annual incidence rate of 172 per 100,000. This was significantly lower than for the Queensland population as a whole (Standard Incidence Ratio 0.79, 95% CI 0.75, 0.82), while cancer mortality rates were significantly higher in Indigenous people (Standardised Mortality Ratio 1.36, 95% CI 1.28, 1.45). Phase Two: Compared to their non-Indigenous counterparts similarly cared for in the public health system, Indigenous people diagnosed with cancer were more socially disadvantaged and had a greater number of comorbidities. Despite being diagnosed with similar stages of cancer, they were less likely to receive any cancer treatment, including palliative treatment, and somewhat less likely to receive curative treatment than their non-Indigenous counterparts. A much greater proportion of Indigenous people than non-Indigenous people who did not receive treatment were found to have comorbid diseases, and to a lesser extent proportionately more Indigenous women received no treatment. Indigenous people experienced worse overall cancer survival when stage, socioeconomic status, and comorbidities were taken into account (HR =1.20, 95% CI 1.05, 1.37) but this survival difference was no longer apparent after treatment uptake was also included in the model. With respect to the three selected study cancers, Indigenous patients with lung cancer were diagnosed with a similar cancer stage and had a greater number of comorbidities. There was no survival disadvantage for Indigenous male patients, however significantly more Indigenous women with lung cancer did not receive treatment and their survival was significantly worse than for their non-Indigenous counterparts. Indigenous patients with head and neck cancers had similar socioeconomic status and number of comorbidities compared to their non-Indigenous counterparts, and there was no significant difference in cancer stage. They received less treatment and their survival was significantly worse even after adjustment for lack of treatment (HR= 1.88 95% CI 1.10, 3.20). Indigenous women with breast cancer had significantly lower socioeconomic status and more comorbidities but stage at diagnosis was similar and in contrast to other cancers studied, Indigenous women with breast cancer were as likely to received cancer treatment and survival was similar to non-Indigenous women. For Indigenous people with cancer overall, and for those with lung, head and neck or breast cancers, who did receive treatment, there was little to no difference in the treatment administered compared to non-Indigenous cancer patients. Conclusions: Overall Indigenous people in Queensland had lower cancer incidence but higher mortality than the overall Queensland population. Among Queenslanders whose circumstances were comparable (excluding those who had treatment only in the private system), Indigenous people with all cancers combined still experienced somewhat worse cancer survival than their non-Indigenous counterparts, largely accounted for by lower socioeconomic status and poorer overall health. Differential survival was not apparent overall after lack of treatment had been taken into account however, differences in treatment and survival varied greatly by cancer type, ranging from significantly worse for Indigenous people with head and neck cancer for example, to no difference for Indigenous women with breast cancer. The lack of cancer treatment associated with observed survival differences in general appeared to reflect the greater comorbidity present in Indigenous cancer patients. Besides attention to alleviation of the underlying disadvantage and poor baseline health of Indigenous people with cancer, greater cross-cultural attention to their health care needs, including the development of culturally appropriate cancer information material, would also seem beneficial in improving the outcomes of Indigenous cancer patients.
Keyword Indigenous, cancer, incidence, mortality, survival, cancer treatment, comorbidities
Additional Notes Colour: 40, 92, 95, 111, 115, 118, 119, 121, 134, 140, 145, 148, 149, 150, 164, 168, 171, 173, 175, 176, 177, 188, 192, 194, 195, 196, 238, 239, 240, 241, 242, 243 Landscape: 84, 86, 104, 105, 111, 115, 121, 134, 140, 150, 164, 171, 173, 177, 192, 193, 196, 249, 250, 251, 252, 253, 254, 255, 256, 258, 259, 261, 262, 263, 264, 265, 269

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