ANALYSIS:The report highlights a need to research patterns of healthcare access and utilisation in Ireland, North and South
WHILE WE have benefited from more than a decade of ever more detailed reports from cancer registries in the Republic and Northern Ireland, this is the first publication of a comprehensive all-island cancer atlas.
Using cancer incidence data for the years 1995 to 2007, the atlas shows some significant geographical variations in cancer risk. Among the most striking is the higher levels of non-melanoma skin cancers in coastal areas. These cancers, unlike the more deadly melanomas, tend to spread locally in the body and are rarely fatal. But they are the most common cancer on the island and so any geographic variation needs explanation.
In general, variation in cancer rates across geographical areas may be attributed to three factors – true geographical variation in the underlying risk of cancer, differences in data collection and definition, and random variation.
Sunshine and exposure to ultraviolet light is the biggest known risk factor for skin cancer; yet the incidence of these cancers is low along the southeast coast, which enjoys the highest sunshine levels across the island. But the higher risk in north and west Kerry and in Newry and Mourne is difficult to explain solely in terms of annual sunshine.
Another major finding is the strong geographical pattern of stomach cancers, with a higher risk in a band running from Dublin to Donegal, excluding the northeast but including Belfast. This cannot readily be explained; the factor most associated with stomach cancer is infection with the bacterium helicobacter pylori (H pylori), but there is no research to suggest that the bug is more common in the areas of highest stomach cancer incidence.
However, as an easily treatable risk factor, there is a need to focus further research on this geographic pattern.
Stomach cancer risk was also higher in areas of high population density and in those with high unemployment and lower educational attainment. Other cancers showed a relationship to employment or education: the risk of lung, stomach, cervical, head and neck cancer was higher in areas of high unemployment and low educational attainment; and the risk of cancers of the skin, female breast and prostate was lower in areas of high unemployment and high educational attainment.
Meanwhile, people living in more densely populated areas had a higher risk of cancer than those living in more sparsely populated areas of the island. And the well-established risk of smoking is reflected in the higher incidence of lung cancer in urban, working-class environments where smoking was more common in the years preceding the data collection for this atlas.
However, the report highlights the relative paucity of information on risk factors such as alcohol and smoking at individual and small area level in both jurisdictions. If this information was available it would make it easier to explain some of the geographic variation revealed by this report.
In turn, it would enable public health initiatives target affected areas in a way that would be more likely to bring about cancer-preventing lifestyle change.
The atlas highlights a need to research patterns of healthcare access and utilisation in Ireland, North and South, to see how these affect cancer risk. Its publication represents a significant step forward in deepening our knowledge of cancer, one of the main causes of death on the whole island.