Socioeconomic factors associated with risk of upper aerodigestive tract cancer in Europe
Introduction
Upper aerodigestive tract (UADT) cancer includes the subsites: oral cavity, pharynx (excluding nasopharynx), larynx and oesophagus. Collectively these cancers are among the most common in the world – with the greatest burden falling upon developing countries.1 Although rarer in Europe, UADT cancers still account for 180,000 new cases per year,2 and the incidence has been increasing in our most deprived communities.2
There is little doubt that tobacco smoking and excessive alcohol consumption are the major risk factors for UADT cancer3, with diets low in fruits and vegetables,4 and human oncogenic papillomavirus infection5 also associated with increased risk. While it is recognised that low individual socioeconomic status (SES) is associated with increased risk,6 the components and pathways of this socioeconomic effect have had limited attention. Few studies examining the effect of socioeconomic factors on UADT cancer have adequately controlled for the known behavioural risk factors, and have simply adjusted for age.6 Previous studies have identified independent effects of social factors having adjusted for smoking and alcohol drinking,7, 8 while others have found that the social effects are completely lost when adjusting for alcohol drinking and smoking.9 One study found that the effects of low social class could be explained by co-existing occupational (toxic) exposures.10
It is almost unheard of to investigate the behavioural risk factors for UADT cancer without adjusting for socioeconomic status. However, for this analysis, in keeping with the classical methods in social epidemiology,11 we flip this logic on its head, and take an alternative perspective a priori – aiming to assess socioeconomic factors both independently and through their influence on behavioural risk factors. Uniquely we aim to extensively adjust for the known behavioural risk factors of smoking, alcohol drinking and diet which would confound any relationship with social factors; and we have the opportunity to utilise one of the largest case–control studies undertaken for UADT cancer aetiology.6, 12 At a time of increased focus on genetic and lifestyle factors associated with cancer – we also feel this is a timely opportunity to take a step back and view a bigger picture of UADT cancer aetiology and the role of the social and economic context of risk.
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Material and methods
The ARCAGE (Alcohol-Related Cancers and Genetic Susceptibility in Europe) multicentre case–control study was conducted in 14 centres in 10 European countries. Full details of study design have been described elsewhere12 and will be only briefly summarised here. Following a common protocol (although slightly different in the Paris centre), cases were defined as those diagnosed with primary squamous cell tumours of the UADT between 2002 and 2005 (Paris: 1987–1992).
Diagnoses included malignant
Results
Overall the ARCAGE study participation rates were 82% (n = 2304) cases and 68% (n = 2227) for controls. In this analysis 2198 cases and 2141 controls were included – 192 subjects were excluded as they had one or more key variables missing for education, smoking, alcohol or diet. The UADT cancer subsite distribution for cases was oral/oropharyngeal (n = 1117, 51%), hypopharynx/larynx (n = 856, 39%) and oesophageal cases (n = 225, 10%). The characteristics of the case and controls are shown in Table 1.
Discussion
Our study demonstrates that wide socioeconomic inequalities in the risk of UADT cancer exist across Europe and they are not fully explained by the traditional recognised lifestyle behaviours of smoking, alcohol consumption and dietary factors. The lowest levels of educational attainment confer an almost doubling of risk associated with UADT cancer, remain significant when we adjust for behavioural factors, and were consistent across the subsites of UADT cancer. Adjustment for behaviours
Conflict of interest statement
None declared.
Acknowledgements
This work was supported by the European Community (5th Framework Programme) [Grant Number QLK1-CT-2001-00182], and the Compagnia San Paolo and AICR (for the Turin center).
We gratefully acknowledge the study interviewers and our clinical colleagues in hospitals and primary care who supported this study. In Glasgow we are indebted to Dr. Gerry Robertson from the Beatson Oncology Center and Mr. John Devine from the Southern General Hospital. GJM and TVM partly worked on this study while at the
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