Relatively little is known of the role of lifestyle and other potentially modifiable factors in prostate cancer aetiology, despite intensive investigation. The use of prostate-specific antigen (PSA) testing on a widespread scale in asymptomatic men has uncovered large numbers of occult carcinomas and has led to increases in incidence rates all over the developed world (Quinn and Babb, 2002). In Ireland, the prostate cancer incidence rate increased markedly over the study period. The consequence has been to mask any differences in underlying risk. The risk of prostate cancer was considerably higher in RoI than in NI and, unlike almost every other cancer, the risk had an inverse relationship with population density. The risk of prostate cancer was also higher in areas with higher education levels.
Mapping of prostate cancer risk in 1995-2001 showed a relatively lower rate of risk in NI compared to RoI and, in RoI, a patchy distribution with no overall pattern. While the rate was high in and around some urban areas, in others (e.g. Limerick) there was no evidence of increased risk. In Dublin, there was a markedly higher risk in the south, and especially the south-west, of the city. This distribution had a closer resemblance to patterns of educational attainment than to unemployment (see Maps 2.4 and 2.5). In 2002-2007 the spatial pattern in RoI showed, to a large extent, an extension of the areas of higher risk to the more rural parts of the country and a lessening of the north-south differential in Dublin city. In NI, some areas of higher risk in the west had disappeared in the later period, but this may be an artefact due to the fact that risk in other areas had increased in 2002-2007.
Although the GP referral guidelines from the National Cancer Control Programme (RoI) (Health Service Executive, 2011) state that “PSA testing of asymptomatic men or PSA screening is not national policy” this seems to have had only a limited impact on practice in RoI, where PSA testing was at a very high level during the period covered by the atlas (Drummond et al., 2010). The differences in overall prostate cancer risk between RoI and NI seem to be determined by higher rates of PSA testing and a lower threshold for prostate biopsy in RoI (Carsin et al., 2010). The changes in geographical patterns of risk within RoI are likely to reflect changes in testing and biopsy rates, due to a combination of awareness and implementation of policy by GPs, demands by patients and investigation rates by specialists. Of interest is the noticeable fall in relative risk between 1995-2001 and 2002-2007 in the former RoI South Eastern Health Board area (counties Waterford, Kilkenny, Wexford, Carlow and Tipperary South). It would be interesting to investigate which, if any of the factors listed above were responsible for this change.
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