Methods and Summary

This report includes 22 maps. There are incidence and death maps for the 11 following cancers – breast, prostate, lung, colon, rectum, melanoma, leukemia, lymphoma, stomach, pancreas and cervix.  All maps show cancer incidence and death for the period 1991-2000.  The rates presented in the maps are annualised rates per 100,000 people.

The maps all use age-sex standardised data. The process of direct standardisation ensures that different age sex profiles for each geographical area are re-calibrated to become directly comparable.  The unit for each dot shown on the map is a statistical local area (SLA), using the 1998 designated boundaries.  For each map 113 SLAs are shown together with 4 unincorporated areas.  There are seven unincorporated areas which are not shown on the maps as either the population of the area is zero or residents of the area cannot easily be distinguished from a neighbouring area (eg. Unincorporated West Coast).

There are a number of problems with mapping cancer data.  Firstly, for some cancers such as lung cancer there is a long latency period between the exposure which caused the disease and the diagnosis of cancer.  This means that people with lung cancer may move location, say from a rural area to a regional centre between exposure and diagnosis, thus inflating the cancer incidence rate of the regional centre.  Secondly, addresses recorded in the South Australian Cancer Registry are not always detailed enough to accurately assign a SLA.  This leads to the loss of about 2% of data and potentially inaccurate assignment of a further 5% of data.

Caution needs to be taken in putting too much weight on individual dots on the maps.  The population used to assign an incidence or death rate varies from over 33,000 in the case of Onkaparinga/Woodcroft in Adelaide’s south to less than 1,000 in Orroroo/Carrieton in the mid north.  With a number of rural SLAs and unincorporated areas have very small populations, the recording of a small number of a particular type of cancer can lead to a high incidence rate.  It is where geographical groupings of dots show a consistent pattern that more accurate interpretations of the data can be made.

There are several clear patterns which emerge on some of the maps.  Firstly, cancers such as breast, melanoma and prostate cancer, which require screening or a medical check for detection, almost always have higher incidence rates in high socio-economic status areas such as eastern and inner southern Adelaide. Secondly, some cancers such as lung and stomach cancer have a well documented link with low socio-economic status and incidence and death rates are higher for northern and western Adelaide, and for rural areas like the Iron Triangle and the Riverland. Thirdly, for the majority of cancers there a no overall differences in incidence and mortality between city and country areas.  The only exception to this is prostate cancer where there is higher mortality in country areas than city areas.

SA Cancer Registry Department of Health Level 3, AGC Building, 162 Grenfell Street, Adelaide, South Australia 5000 Telephone: (08) 8226-6158 or (08) 8226-6337  | Facsimile: (08) 8226-6291 E-mail address: Epidemiology@health.sa.gov.au Postal address: PO Box 6 Rundle Mall, Adelaide 5000