Adjusted rates for geostatistical analysis

In this section, the adjusted rates for the five types of cancer are considered to identify the difference of cancer distribution in Perth SLAs. First, we look at the maps of the age-adjusted and age-sex-age-adjusted rates for lung, melanoma and colorectal cancers.

For the overall incidence rates, Figure 7 indicates that lung cancer incidence is relatively low compared with melanoma and colorectal (CRC) cancer and the difference between age-adjusted and age-sex-age-adjusted rates is slight. Higher melanoma cancer incidence rates arise mainly in the western part of the Perth metropolitan area. Higher colorectal cancer incidence rates occur mainly in the north-west of the Perth metropolitan area and in the suburbs near Perth.

Age-adjusted rates Age-sex-adjusted rates Lung cancer incidence

66.23 48.52 45.72 44.14 42.25 41.34 38.58 35.64 34.28 31.24 Melanoma incidence

92.55 63.12 56.42 51.40 47.51 44.55 43.09 41.29 39.09 35.82 CRC incidence

92.41 60.48 58.55 56.98 53.75 52.25 50.21 47.81 45.87 42.00 Figure 7 Adjusted rates for cancer incidence.

For the incidence rates by sex, Figure 8 indicates that the difference between males and females is relatively strong for lung cancer compared with melanoma and colorectal cancers. Males and females have relatively low lung cancer risk compared with melanoma and colorectal cancers. Lung cancer adjusted rates of males are much higher than those of females in most areas. For melanoma, the difference between males and females is slight.

For colorectal cancer, the highest incidence rate is 130 per 100,000 person-years for males during the period 1990-2005 but only 90 for females.

Male Female Figure 8 Cancer incidence rates by sex, 1990-2005.

Although lung cancer incidence rates are lower than other cancer rates, the mortality rates for lung cancer are relatively high according to Figure 9. Compared with incidence rates, the two mortality adjusted rates are quite similar. This indicates that age and sex probably have less influence on cancer mortality than on incidence. For melanoma cancer, the rates are much lower than for other cancer types. During the 16-year period, the highest mortality rate is 17 per 100,000 person-years across the Perth metropolitan area. However, the rate is 56 for lung cancer and 38 for colorectal cancer. For colorectal cancer, the mortality rates around Perth metropolitan are relatively high.

Age-adjusted rates Age-sex-adjusted rates Lung cancer mortality

55.68 42.49 40.22 38.42 36.45 34.18 32.69 29.42 27.71 25.56 Melanoma mortality

16.80 7.29 6.28 5.53 5.13 4.75 4.60 4.23 4.07 3.75 CRC mortality

37.83 25.57 23.86 22.98 21.94 21.48 20.14 19.14 18.48 16.67 Figure 9 Adjusted rates for cancer mortality.

In Figure 10 the development with time of the mortality rates is shown. We see that there is an overall increase on the lung cancer rates in the Perth metropolitan area. For melanoma, it seems that there is a slight increase in mortality rates in most areas over three periods. For colorectal cancer, the change is slight. It seems that higher colorectal cancer rates are mainly near the inner city suburbs in each period.

1990-1995 1996-2000 2001-2005 Lung Cancer mortality

70.35 46.24 41.53 38.54 36.11 32.78 29.03 25.12 23.09 19.75 Melanoma mortality

53.76 8.83 7.08 6.17 5.57 4.74 4.11 3.57 3.02 1.96 CRC mortality

49.40 30.47 27.06 25.11 23.07 21.05 19.35 17.19 15.45 12.21 Figure 10 Age-adjusted rates for cancer mortality during three time periods.

Next we will consider the maps of the age-adjusted rates for sex specific cancers: breast and prostate cancers. For the incidence, overall prostate cancer incidence rates are relatively high compared with breast cancer in western part of the Perth metropolitan area (Figure 11).

However, breast cancer rates are higher than prostate cancer rates in most of the eastern part of the study area. The overall higher rates arise in the inner suburbs of Perth. Based on Figure 7 and Figure 11, it can be seen clearly that breast cancer incidence is the most common cancer risk for females while the most common incidence risk for males is prostate cancer. For the mortality, it seems that breast cancer has higher overall mortality rates than others in western part of Perth metropolitan area. Generally speaking, the sex

specific cancer mortality rates are relatively low compared with lung cancer mortality (Figure 9).

Breast Cancer Prostate cancer

Incidence 90-05

314.55 153.01 138.24 129.06 120.74 113.98 108.25 101.39 97.42 85.10 Mortality 90-05

48.48 33.57 28.55 26.61 24.69 23.36 20.75 18.81 17.69 15.41 Figure 11 Age-adjusted rates for breast and prostate cancer in 1990-2005.

The cancer rates for the three time periods 1990-1995, 1996-2000 and 2001-2006 are shown in Figure 12. Breast cancer incidence increases steadily in these three periods in the Perth SLAs and the incidence is higher in the inner suburbs of metropolitan Perth. For prostate cancer incidence, it seems that there was a slight decrease in cancer rates around Perth metropolitan by the second period and a significant increase in cancer rates across Perth metropolitan area by the third period.

In comparison, higher mortality rates for breast cancer mortality are mainly in areas close to Perth city centre where the rates kept decreasing with time. However, mortality rates increased in other areas in three time periods. For prostate cancer, the overall mortality rates are relatively high in the second period and low in the third period.

1990-1995 1996-2000 2001-2005

Figure 12 Age-adjusted rates for breast and prostate cancer in three time periods.

From the discussions above, it can be seen that males have a much higher lung cancer incidence risk than females but they have quite similar incidence risk for melanoma and colorectal cancers. The lung cancer incidence risk is lower than melanoma and colorectal cancer risks for both males and females. However, lung cancer mortality risk is much higher than melanoma and colorectal cancer mortality risk. Although people have a very high melanoma cancer incidence risk, the mortality risk is very low compared with other cancers.