THE RISK of developing many forms of cancer is “significantly higher” in the Republic than in Northern Ireland, according to a 13-year study of cancer prevalence on the island.
The All-Ireland Cancer Atlas, published today, analysed the geographical variation of 18 forms of cancer in the years 1995 to 2007 inclusive, and found major differences in the risk of many cancers across the island.
The study, a collaboration between the National Cancer Registry and the Northern Ireland Cancer Registry, also examined the cancer risks of both sexes and the risks based on socio-economic factors such as employment and educational attainment.
The most conspicuous difference was in the prevalence of prostate cancer diagnosis, which was almost 30 per cent lower in Northern Ireland than in the Republic.
Melanoma skin cancer risks were 8 per cent lower for men and 14 per cent lower for women in Northern Ireland; risk of leukaemia was 23 per cent lower for men and 17 per cent for women; pancreatic cancer was 11 per cent lower in men and 22 per cent lower in women; risk of bladder cancer was 8 per cent lower for men and 14 per cent lower for women; and the risk of brain and other central nervous system cancers was 10 per cent lower for men and 20 per cent lower for women in Northern Ireland.
Just one of the cancers assessed showed a greater risk for men and women in Northern Ireland. The risk of lung cancer was significantly higher in Northern Ireland for men – 11 per cent higher – while for women the risk was 7 per cent higher.
With certain cancers the geographical difference was apparent in one gender only. There was no statistically significant difference between men North and South for head and neck cancer, but for women the risk was 21 per cent higher in Northern Ireland. Similarly, women in the North had a 14 per cent higher risk of non-Hodgkin’s lymphoma, but there was no significant difference for men.
The risk of oesophageal cancer was 8 per cent lower in Northern Ireland women, but again there was no real difference between men North and South.
There were also cross-Border variations between cancers that affect only women. The risk of cancer of the uterus showed no significant variation with socio-economic variables or population density, but was 11 per cent higher in the North than in the Republic. Cancer of the cervix, which was more prevalent among unemployed women and those with lower educational attainment, as well as in densely populated areas, was 11 per cent higher in the Republic.
Likely explanations were available for some of the geographical differences. In relation to prostate cancer, a test known as the prostate specific antigen test was far more commonly used in the Republic than in Northern Ireland during the period assessed.
A rich/poor divide also gave indications as to the greater risks of certain cancers. Skin cancers were higher among people with jobs, who were more likely to be able to afford holidays, while smoking-related cancers were more common among lower socio-economic groups.
However, the report found much of the geographical difference was “not explicable” solely in socio-economic or demographic terms. “Few of the geographical patterns could be satisfactorily explained by the available data on risk factors,” it said.
Due to a lack of research information, in many cases it was only possible to speculate as to the origins of increased risk. In areas where there was excess risk of particular cancers, it was likely that intervention could help to address these risks. “Action is needed urgently to determine the causes of excess risk,” the report said.
A restrictive approach to information-sharing, which was not always justified by legislation or data protection guidelines, had made linking cancer data with occupational or census data in both jurisdictions “almost impossible”.
Much better information was needed in relation to risks and the determinants of risk. Areas of unexplained higher risk should be studied in detail, while research into the levels of awareness of cancer risks also required greater study, the report found.
