Cancer

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Cancer

The impact of cancer on Indigenous people has attracted much less attention than it deserves, for two main reasons. First, the level of identification of Indigenous people in cancer notifications is known to be poor [1][2]. Indigenous identification in the registries has been improving [3][4], but there are currently no national data on cancer incidence in Indigenous people due to poor data quality in several jurisdictions [5]. For those Indigenous patients who are registered with cancer, there is concern that not all are correctly identified as Indigenous [2]. Provision for the identification of Indigenous people is not yet included on all pathology forms and the extent to which Indigenous cancer patients are identified in hospital inpatient statistics varies across Australia [4]. Second, the fact that cancer has often been reported in terms of the proportions of deaths it causes (19% of Indigenous deaths compared with around 30% of non-Indigenous deaths in Australia in 2009 [6]) rather than by rates has tended to give the erroneous impression that cancer does not have a great impact among Indigenous people. Analysis of rates – rather than simple comparison of proportions – reveals that cancer deaths are around 45% more common among Indigenous people than among non-Indigenous people [1].

Extent of cancer among Indigenous people

Incidence

During 2003-2007, an average of 458 Indigenous people living in Qld, WA, SA and the NT were diagnosed with cancer each year [5]. ⁵ After adjusting for differences in the age structures of the two populations, cancer incidence rates were lower for Indigenous people than for non-Indigenous people during this period (385 and 433 cases per 100,000 people, respectively).

The most common cancer diagnosed among Indigenous people for the 2003-2007 period was lung cancer (average of 71 cases per year), and the second most common was breast cancer (among Indigenous females) (average of 49 cases per year) [5]. Earlier data for the period 2000-2004 revealed that more new cases of cancer were reported among Indigenous females (1,598) than among Indigenous males (1,485), a contrast to the pattern for non-Indigenous people, for whom new cases are more common among males than females [7].

In terms of specific cancers, age-standardised incidence rates for Indigenous people living in NSW, Vic, Qld, WA, SA, Tas and the NT in 2007 were higher for lung cancer and cervical cancer (in Indigenous females) than for their non-Indigenous counterparts [8]. In 2003-2007 the incidence rate for cervical cancer was almost three times higher for Indigenous females than for non-Indigenous females (18 and 7 cases per 100,000 females, respectively) [5]. Despite being the most commonly reported cancer among Indigenous women each year between 2002 and 2006 in Qld, WA, SA and the NT, Indigenous women were significantly less likely to be diagnosed with breast cancer than were non-Indigenous women (69 and 103 new cases per 100,000 women, respectively), but death rates did not differ significantly [9].

Recent comparable data for other cancers are not available, but data for 2000-2004 reveal that Indigenous males and females had higher age-standardised incidence rates than did their non-Indigenous counterparts for lung cancer; cancers of the liver and gall bladder; pancreas; cancers of the mouth and throat; oesophagus; and cancer of unknown primary site (Table 15) [7]. Age-standardised incidence rates were lower for Indigenous males and females than for their non-Indigenous counterparts for colorectal cancer and lymphomas. Rates for breast cancer were lower for Indigenous females than for non-Indigenous females and rates for prostate cancer were lower for Indigenous males than for non-Indigenous males.

Table 15: Age-standardised incidence rates for selected cancers, by sex and Indigenous status, and Indigenous:non-Indigenous rate ratios, NSW, Vic, Qld, WA, SA and the NT, 2000-2004

Cancer	Males			Females
	Indigenous	Non-Indigenous	Ratio	Indigenous	Non-Indigenous	Ratio
Source: ABS and AIHW, 2008 [7]
Notes: Rates per 100,000 population Ratio is the Indigenous rate divided by the non-Indigenous rate Due to the incomplete identification of Indigenous status, these figures probably under-estimate the true difference between Indigenous and non-Indigenous rates
Lung	91	61	1.5	44	28	1.6
Breast	-	-	-	85	115	0.7
Prostate	56	141	0.4	-	-	-
Colorectal	40	76	0.5	37	52	0.7
Lymphoma	43	59	0.7	22	39	0.6
Unknown primary site	31	19	1.7	27	14	1.9
Mouth and throat	26	11	2.2	11	11	1.1
Liver and gallbladder	21	10	2.1	14	5	2.6
Pancreas	16	11	1.5	12	9	1.4
Oesophagus	17	8	2.0	4	3	1.3
Cervix	-	-	-	17	7	2.4

Mortality

In 2009, cancer was the underlying cause of 465 deaths of Indigenous people across Australia [6]. The median age of death with an underlying cause of cancer was 62.7 years for Indigenous people and 75.3 years for non-Indigenous people.

Cancer was the second most common cause of death for Indigenous people living in NSW, Qld, WA, SA and the NT in 2004-2008, exceeded only by deaths from CVD [10]. The death rates for cancer among Indigenous males and females were higher than among their non-Indigenous counterparts (1.2 and 1.5 times higher, respectively) and death rate ratios were higher for cervical cancer (4.3), lung cancer (1.7), and digestive organ cancers (1.4) for Indigenous people than for their non-Indigenous counterparts. Death rates for cervical cancer in 2004-2008 had slightly decreased since 2003-2007, when Indigenous women died at over five times the rate of non-Indigenous women (9.9 compared with 1.9 per 100,000 women) [10][11]. For breast cancer, death rates were similar for the two populations in 2004-2008 [12].

The patterns of Indigenous cancer incidence and mortality are largely explained by the higher prevalence of risk factors, most notably tobacco use [13][14][15]. For example, high rates of smoking are the likely cause of a high incidence of cancers of the lung, mouth and throat [7]. The unusual situation of Indigenous people having lower incidence rates and higher death rates for cancer than do non-Indigenous people could be due to a number of factors. First, Indigenous people could have higher case-fatality rates than do non-Indigenous people: this could reflect differences between the two populations in the proportions of cancers with high case-fatality rates [2][16][17][18]. Second, cancers could be detected at a more advanced stage among Indigenous people than among non-Indigenous people. Third, there could be differences between Indigenous and non-Indigenous people in treatment outcomes by stage of diagnosis. From the available information, Indigenous people are: significantly more likely to have cancers that have a poor prognosis; usually diagnosed with cancer at a later stage; less likely to receive optimal treatment; and are more likely to die from cancers than other Australians [2].

References

1. Roder D (2007) Epidemiology of cancer in Indigenous Australians: implications for service delivery. Paper presented at the 9th National Rural Health Conference: standing up for rural health: learning from the past, action in the future. 7-10 March 2007, Albury, NSW
2. Cunningham J, Rumbold AR, Zhang X, Condon JR (2008) Incidence, aetiology, and outcomes of cancer in Indigenous peoples in Australia. Lancet Oncology; 9(6): 585-595
3. Zhang X, Condon JR, Rumbold AR, Cunningham J, Roder DM (2011) Estimating cancer incidence in Indigenous Australians. Australian and New Zealand Journal of Public Health; 35(5): 477-485
4. Australian Institute of Health and Welfare (2010) Australia's health 2010: the twelfth biennial report of the Australian Institute of Health and Welfare. Canberra: Australian Institute of Health and Welfare
5. Australian Institute of Health and Welfare (2010) Cancer in Australia 2010: an overview. Canberra: Australian Institute of Health and Welfare
6. Australian Bureau of Statistics (2011) Causes of death, Australia, 2009. Canberra: Australian Bureau of Statistics
7. Australian Bureau of Statistics, Australian Institute of Health and Welfare (2008) The health and welfare of Australia's Aboriginal and Torres Strait Islander Peoples 2008. Canberra: Australian Bureau of Statistics and Australian Institute of Health and Welfare
8. Steering Committee for the Review of Government Service Provision (2011) Report on government services 2011: Indigenous compendium. Canberra: Productivity Commission
9. Australian Institute of Health and Welfare, National Breast and Ovarian Cancer Centre (2009) Breast cancer in Australia: an overview, 2009. Canberra: Australian Institute of Health and Welfare
10. Australian Institute of Health and Welfare (2011) Aboriginal and Torres Strait Islander health performance framework 2010: detailed analyses. Canberra: Australian Institute of Health and Welfare
11. Australian Institute of Health and Welfare (2010) Cervical screening in Australia 2007-2008: data report. Canberra: Australian Institute of Health and Welfare
12. Australian Health Ministers’ Advisory Council (2011) Aboriginal and Torres Strait Islander health performance framework: 2010 report. Canberra: Office for Aboriginal and Torres Strait Islander Health, Department of Health and Ageing
13. Threlfall TJ, Thompson JR (2009) Cancer incidence and mortality in Western Australia, 2007. Perth: Department of Health, Western Australia
14. Condon JR, Barnes T, Cunningham J, Armstrong BK (2004) Long-term trends in cancer mortality for Indigenous Australians in the Northern Territory. Medical Journal of Australia; 180(10): 504-511
15. Condon J (2004) Cancer, health services and Indigenous Australians. Canberra: Office for Aboriginal and Torres Strait Islander Health, Cooperative Research Centre for Aboriginal and Tropical Health
16. Roder D, Currow D (2009) Cancer in Aboriginal and Torres Strait Islander people of Australia. Asian Pacific Journal of Cancer Prevention; 10(5): 729-733
17. Miller J, Knott V, Wilson C, Cunningham J, Condon J, Roder D, Bowden J, Chong A, Doherty T, Griffiths K, McNamara C, Miller C (2010) Aboriginal and Torres Strait Islander cancer control research project. Canberra: Cancer Australia
18. Valery PC, Coory M, Stirling J, Green AC (2006) Cancer diagnosis, treatment, and survival in Indigenous and non-Indigenous Australians: a matched cohort study. The Lancet; 367(9525): 1842-1848

Endnote

5. The overall level of missing data on Indigenous status for cancers diagnosed between 2003 and 2007 was 11%.

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