The modelled estimates in the Australian Cancer Atlas are reported in relation to the Australian average. The Australian average is represented by the value of one. That means, if one area has a SIR (Standard Incidence Ratio) of 1.3, then that means that the average rate of that cancer being diagnosed in that area is 1.3 times the Australian average, or 30% higher.
Similarly, if an area has an SIR estimate of 0.8, then that means that the average rate of that cancer being diagnosed in that area is 0.8 times the Australia average, or 20% lower.
However, to understand the cancer burden in a particular area you need more than just one statistic. There are many factors that contribute to how many people are diagnosed with cancer, and how long they survive – some factors are known, some are not. However, they all impact on when a cancer develops in an individual, whether that cancer is detected and diagnosed, and whether that cancer progresses and leads to death. For these reasons, the observed cancer statistics will vary from year to year, or area to area, leading to some ‘fuzziness’ around the true value. Generally, this uncertainty is higher when the population, or the numbers of cancer cases are low.
