Public Health Bulletin Edition 1, 2004 - SA Health - SA.Gov.au

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Ethnic and racial differences in cancer incidence in South Australia David Roder Head Cancer Statistics Unit Centre for Cancer Control Research The Cancer Council South Australia All cancer types South Australians born overseas had an agestandardised cancer incidence about 8% lower than that of the Australian-born during 1977-2000. Among residents born in Southern Europe and Asia, the incidence was about 20% and 23% lower, respectively. Additional details are provided by sex in Figures 1 & 2. Aboriginal and non- Aboriginal residents had similar incidence rates for all cancers collectively, although there were differences by cancer type, some of which are described in this article. Background There are marked differences in cancer incidence around the word. 1, 2 Although genetic factors do contribute, most differences are attributed to variations in lifestyle and environmental exposure. 2-4 Broad inferences can be drawn about the proportion of the cancer burden that is potentially preventable through environmental and lifestyle change. For example, cancer incidence in Africa and Asia, excluding non-melanoma skin cancers, is generally about half the incidence in Australia, and so it would appear that at least 50% of Australian cancers could be preventable. 1 Migrant groups tend to have cancer profiles similar to those of their parent countries when first they arrive in adopted homelands, but these profiles typically approach those of their new countries over time, reflecting lifestyle adaptations and the effects of local environmental exposure. 5 Migrant studies have been a rich source of information about the contributions to cancer risk of changes in social, behavioural and environmental factors. 5 Data on incidence by ethnicity and race are also relevant when planning preventive, screening and treatment services to better address the needs of culturally diverse groups. Introductory background information is now provided on ethnic variations in cancer incidence in South Australia. Further details are available directly from the Epidemiology Branch (details below), or from the website of the Department of Health at: http://www.health.sa.gov.au/pehs/cancer-report-02/cancerreport-2002.pdf or Cancer Council South Australia, at: http://www.cancersa.org.au/i-cmspage=1.7.792 Cancers with a higher incidence in the Australian born Lip cancers and melanomas were generally two to three times more common in the Australian than in the overseas born, reflecting lifelong sun exposure. 4 However, Aboriginal residents were seldom affected, due to the protective effects of skin colouring. 4, 6 Residents born in Asia had an incidence almost 90% lower than that of the Australian born. Cancers of the mouth, throat and oesophagus had an incidence about 40% higher in Australian than in overseas born, with Aboriginal residents showing an incidence about three to four times higher than other South Australians. Particularly low incidence figures applied to residents from Southern Europe. Risk factors for these cancers include tobacco smoking, high alcohol intake, and diets deficient in fruit and vegetables. 3, 4, 7, 8 Large-bowel (colon/rectum) cancers had an incidence almost a quarter higher in Australian than in overseas born, although Aboriginal residents had a comparatively low incidence. Risk factors for these cancers include diets low in vegetables and potentially those high in processed meat and fat. 3, 4, 7, 8 A lack of exercise and excess body weight are thought to contribute further risk. 7 Residents born in Asia and Southern Europe had an incidence about a third lower than that of the Australian born. The incidence of female breast cancer was about 9% higher for Australian than for overseas born, with particularly low rates applying to residents from Southern and Eastern Europe (about 30% lower than for the Australian born). Aboriginal women had an incidence about half that of their non-Aboriginal counterparts. Earlier age at time of first full-time pregnancy is a protective factor for this cancer, and it is likely this would have contributed to the lower incidence in the Aboriginal population. 4 19
Prostate cancer had an incidence about a third higher in Australian than in overseas born, with particularly low rates occurring in males from Southern Europe and Asia. The incidence was about 80% lower in Aboriginal than non-Aboriginal males. Prostate-specific antigen testing is thought to be less common among Aboriginal residents, such that more of their lesions would remain undisclosed. 9 The incidence of testicular cancer tended to be higher (about 20% higher) in Australian than in overseas born men. Again, very low rates applied for males from Asia and Southern Europe. The reasons for these variations are not known, although sedentary lifestyles may be a risk factor, and, possibly, pre-natal exposure to female sex hormones. 3, 4, 9 The Australian born had a higher lymphoma incidence than the overseas born - about 20% higher for non- Hodgkin’s lymphoma and 40% higher for Hodgkin’s disease. Aboriginal residents had relatively few cancers of these types. Lymphomas have been linked to a malfunctioning immune system, as may result from HIV or other viral infections, chemotherapy, or medically induced immunosuppression to avoid rejection of transplanted organs. 4, 10 Cancers with a higher incidence in the overseas born The incidence of cancers of the nasopharynx was about 70% higher in the overseas born than in the Australian born. Among the Asian born, the incidence was 9-10 times higher. This may reflect the consumption from an early age in some parts of Asia of fish, salted according to local tradition - as practised in Southern and South Eastern China. 3, 4, 8 There is also a risk association with Epstein Barr virus infection, which may be causal. 3 The incidence of stomach cancer was approximately 74% higher in the overseas born, with particularly high rates occurring in residents from Eastern Europe, Germany and Southern Europe. Aboriginal residents had an incidence approximately twice as high as other South Australians. A high salt intake has been implicated, whereas diets rich in fruit and vegetables are thought to be protective. 3, 4, 7, 8 Infection with Helicobacter pylori is an additional risk factor. 3 cancer incidence was almost a third higher in overseas than in Australian born, with the highest rates occurring in residents from Northern Europe. Aboriginal residents had a risk almost 50% higher than other South Australians. Tobacco smoking is the predominant risk factor, although contributions from occupational exposures to asbestos and other carcinogens would also apply. 4 Notably, cancers of the pleura (mesotheliomas) had an incidence almost 70% higher in the overseas born, reflecting more common histories of asbestos exposure.4 The incidence of cervical cancer was about twice as high in women from Germany, and about 40% higher in those from other Northern European countries, than for the Australian born. Aboriginal women had a very high incidence - about four times higher than for non-indigenous females. Cervical screening can prevent about 90% of squamous cell carcinomas of the cervix by detecting precursor lesions for pre-emptive treatment. 4 These services need to be culturally sensitive if there is to be a high coverage of the female population. Other cancers more common in the overseas born included bladder cancer (about 20% more common), where tobacco smoking would have contributed, and possibly past exposure to workplace carcinogens and a historical use of phenacetin analgesics. 3, 4, 9 The incidence of thyroid cancer was about twice as high in the Asian as in the Australian born, probably due to excesses or deficiencies in dietary iodine. 4 Concluding comments Cancer rates vary markedly by ethnicity and race. These epidemiological differences provide aetiological clues and should be taken into account when planning culturally appropriate cancer services. The four-fold incidence of cervical cancer among Aboriginal when compared with non-Aboriginal women is one of several elevations that deserve special attention, given the potential for cervical screening to detect precursor lesions and resulting interventions to prevent the development of invasive cancer. Lung Liver cancer was almost 50% more common in the overseas born, with residents from Asia having an incidence about six times higher than that of the Australian born. Aboriginal residents also were at very high risk, with an incidence about seven times higher than for the non-indigenous population. Risk factors include high levels of endemic hepatitis B and C infection, and alcoholinduced cirrhosis. 3, 4, 7 20
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Public Health Bulletin Edition 1, 2004 - SA Health - SA.Gov.au

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