21.2.9 - 21.2.18 Other cancers

21.2.9      Bladder cancer

The risk of bladder cancer in RoI was higher than in NI. The risk of bladder cancer increased with population density but had only a weak relationship to unemployment or education levels for either men or women. For women, there were areas of higher risk in and around the major urban areas of Belfast, Dublin, Cork and Limerick, but not Derry or Galway. The area of higher risk around Limerick was unusual, as Limerick was not consistently among the urban areas with higher risk for other cancers. There was no clear geographical distribution in Dublin, but in Belfast the highest risk was in the east and central part of the city. An almost identical urban pattern was seen for men.

Outside the cities, both men and women had a higher risk on the east coast from Dublin to Wicklow, particularly for men, and in north and west Kerry, particularly for women. There was a high male risk in Donegal and the Ards peninsula, much less so for women.

Bladder cancer risk has been strongly linked to tobacco smoking (Secretan et al., 2009) and there was a limited degree of similarity between the distribution of lung cancer and bladder cancer. Occupational exposure is also an important risk factor (Baan et al., 2009). While most exposures are now controlled, historical exposure to occupational carcinogens (for instance in the chemical, rubber, dyeing and tanning industries) may be responsible for some of the variation seen; there is little information on historical exposures in Ireland.

21.2.10    Head and neck cancer

Head and neck cancer is a heterogeneous group of cancers, but with a largely shared aetiology in tobacco and alcohol use (Secretan et al., 2009). In recent years, human papilloma virus infection is likely to have been responsible for an increasing number of cases, particularly cancers of the tonsil (International Agency for Research on Cancer, 2011b).

The risk of head and neck cancer was higher in NI for women but not men. For both sexes there was a strong relationship to unemployment levels, but not to education. For women there was a band of higher risk extending from north Dublin through Louth into Fermanagh. The areas of highest risk, however, were around Belfast, Derry and on the Inishowen and Dingle peninsulas.

For men, the geographic pattern was very different to that observed for women. There was a patchy distribution of higher risk areas, including most major cities and adjoining areas and a number of sparsely populated areas along the west coast. The pattern of risk more closely resembled that of bladder cancer than lung cancer.

The patterns seen most likely reflect a complex interaction between smoking and alcohol use. The consumption of home-distilled alcohol (poitín) in the past may also have been a factor in rural areas. Dentists have a role in detection of pre-malignant lesions and early oral cancers; residents of more deprived areas (Lang et al., 2008) and those with primary education only (Woods et al., 2009) use dentists less and this may be a factor in areas of higher risk.

21.2.11    Leukaemia

There was a markedly higher risk of leukaemia in RoI than in NI, a surprising finding given the low level of international variation in Europe and the paucity of modifiable risk factors, other than smoking (Secretan et al., 2009). Some ascertainment bias may exist with respect to chronic lymphocytic leukaemia (CLL), which comprises over 40% of all leukaemias, affects older patients and may be asymptomatic for much of its course. It is often detected only through routine blood counts and only picked up if the individual presents to clinical services. However, it is not clear how these factors would differ between NI and RoI. We could find no information on either GP consultation rates or routine blood count rates for older persons in NI and RoI. Socio-demographic variables were poorly correlated with leukaemia risk; the risk was higher especially for men and women in areas with a higher proportion of older persons living alone. The significance of this finding is obscure.

For both men and women the geographical pattern was of a smooth gradient in risk; lowest in the north-east and highest in the south-west. For men in particular the area of highest risk seemed to centre on Limerick and Clare rather than the extreme south-west and for both sexes there was a secondary area of higher risk extending from south Dublin to Wexford, with the highest risk around Wicklow town.

The north-east to south-west gradient could possibly be due to differences in health service utilization between NI and RoI which impacted on detection of asymptomatic CLL. However, when such a difference between countries was simulated in the smoothing process it gave rise to a much sharper gradient in risk at the border than was seen in the leukaemia maps.

21.2.12    Pancreatic cancer

The risk for pancreatic cancer, which is associated with tobacco and heavy alcohol use (Secretan et al. 2009), was significantly higher in RoI than in NI for men and women. Pancreatic cancer is rapidly fatal and the diagnosis is not always confirmed before death, so there is more uncertainty with regard to the reliability of diagnosis than for most other cancers. However, mortality rates in 1995-2007 were also higher for both men and women in RoI than in NI (International Agency for Research on Cancer, 2011c).

For men, the risk fell (but not significantly) with increasing population density but increased with increasing unemployment. For women, on the other hand, the risk was unrelated to population density or unemployment but was higher in areas with a lower level of educational attainment.

The overall geographical pattern was, however, similar for men and women—a smooth gradient from the lowest levels in the north-east to the highest in the south-west, centred, for women, in north Kerry and, for men, on Cork city. For women, there appeared to be a higher risk in central and north Dublin city, but a uniformly low risk in Belfast. For men, the risk in Dublin city was low relative to the rest of the country; although the risk was also low in Belfast, the city centre had a slightly higher rate than the outskirts.

21.2.13    Kidney cancer

The important aetiological factors for kidney cancer are smoking (Secretan et al., 2009) and obesity (World Cancer Research Fund/American Institute for Cancer Research, 2007). The risk of kidney cancer was slightly (but not significantly) lower in NI than in RoI for men, but not women. There was a weak upward trend in risk with population density for women but no other relationship to socio-demographic variables.

While for both sexes there was an area of higher risk along the east coast—in Wicklow, Dublin, Meath and Louth—the overall pattern of risk was different for men and women. For women, there was an extensive area of higher risk in northern NI, while for men the risk in NI was lower, apart from Fermanagh. For men there was an extensive area of higher risk in the east midlands, extending into Galway, with the highest risk in Offaly. There was no clear intra-urban pattern for either sex.

Increasing numbers of kidney cancers are being detected incidentally in the course of abdominal scans for other disease (Hock et al., 2002; Falebita et al., 2009) and this may affect geographical patterns.

21.2.14    Oesophageal cancer

Cancer of the oesophagus consists of two main histological types—squamous carcinoma and adenocarcinoma—which differ somewhat in their underlying causes. While both are related to tobacco and alcohol consumption (Secretan et al., 2009), only adenocarcinoma is related to obesity (World Cancer Research Fund/American Institute for Cancer Research, 2007). As the analyses in this atlas combine these cancer types, this might have obscured some patterns specific to one or other histological type.

For both men and women there was an increase in risk with increasing population density and for men, a weak relationship to unemployment.

The pattern of distribution of oesophageal cancer was similar for men and women. The highest risk in the urban areas was in Dublin and Belfast city centres, although the female risk was lower in Belfast than Dublin. There was no area of high risk associated with other urban centres, other than the region around Cork.

Outside Dublin and Belfast, there seemed to be three main foci of higher risk—the largest around Cork city, extending, for women, to the east and west and, for men, to the north, into Tipperary. The second focus was in south Dublin and Kildare and was more defined for men than for women. The third area was smaller, involving Larne, Belfast, Ards and (for men) north Down. There were also two small areas of higher risk for men around Drogheda and Dun Laoghaire.

21.2.15    Ovarian cancer

Family history is the most important risk factor for ovarian cancer (Stratton et al., 1998); potentially modifiable risk factors include nulliparity, age at first pregnancy and number of pregnancies (Ness et al., 2002; Nagle et al., 2008; Jordan et al., 2007). Obesity may also be a risk factor (Schouten et al., 2008). The risk was similar in RoI and NI, and none of the socio-demographic variables studied appeared to correlate with risk.

The incidence of ovarian cancer is particularly high in Ireland and the UK compared with many other developed countries. However, differentiation between frankly malignant and “borderline” ovarian cancer (which is not registered by some cancer registries) is sometimes difficult to make; the resulting variations in registration may contribute to differences in recorded rates internationally.

Two areas of higher risk were found; one to the east of Cork city extending through most of Cork and Waterford, and the other a more diffuse area in NI encompassing Moyle, Ballymoney and Ballymena, Dungannon/Craigavon, Down and part of Newry and Mourne. The relative risk was low in the Belfast area.

The pattern of risk bears some resemblance to that of colorectal cancer, which also was poorly correlated with socio-economic variables, as well as to oesophageal cancer; the latter, however, was also related to population density and unemployment.

21.2.16    Brain and other central nervous system cancers

The aetiology of brain and other central nervous system cancers is largely unknown. There is very little international variation apart from the high incidence in the Nordic countries, and, within Ireland, there was only a minor degree of geographical variation. For both men and women there was a gradient of risk, lowest in the north-east and highest in the extreme south-west, reflected in an overall higher risk in RoI. The extent of variation was greater for women than men but otherwise the patterns were almost identical.

21.2.17    Cancer of the corpus uteri

Modifiable risk factors for cancer of corpus uteri include obesity (World Cancer Research Fund/American Institute for Cancer Research, 2007), nulliparity (Dossus et al., 2010) and use of hormone replacement therapy and tamoxifen (International Agency for Research on Cancer, 2011a). The risk of uterine cancer was higher in NI than RoI but showed no significant relationship to any of the socio-demographic variables studied. The geographical pattern was unusual, with two areas of higher risk—one in the eastern part of NI, with the highest rate in Newry and Mourne; the other in the west, with the highest rate in west Mayo, extending into Galway and Sligo. An area of higher risk was also noted in Kerry.

International variations in uterine cancer incidence reflect, to some extent, variations in the prevalence of hysterectomy (Bray et al., 2005). However, we are not aware of any data on the frequency of hysterectomy in NI compared to RoI, or within either country.

21.2.18    Cancer of cervix uteri

The risk of cervical cancer was higher in RoI than in NI, and the incidence rate was relatively high by international standards. The risk was strongly correlated at an area level with increasing population density, unemployment and low educational achievement. A population-based screening programme has been in existence in NI for many years, with all eligible women invited regularly since 1993. In RoI, by contrast, national population-based screening did not begin until 2008, although considerable opportunistic screening has been done for some time.

The highest risk in Belfast was in the north and west of the city, as well as in the city centre, while in Dublin the city centre had the lowest risk. Outside the two major cities there was a large area of higher risk in Kildare, Wicklow and Wexford, an area of higher risk to the north and east of Belfast, and a more diffuse area between Cork and Waterford cities. This distribution was broadly similar to that of lung cancer in women, reflecting their common association with both deprivation and smoking. Prior to the introduction of population-based screening in RoI, the uptake of screening was higher in areas with higher socio-economic status (Walsh et al., 2011); this dependence on socio-economic status appears to be a characteristic of opportunistic screening, as compared to population-based programmes (Walsh et al., 2010).

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