Regional variations in testicular cancer rates in Ireland: clusters and communities

Abstract

We welcome Alsinnawi et al.’s [1] paper on rates of testicular cancer. However, the authors imply an association with persistent organic pollutants (POPs), particularly polychlorinated biphenyls (PCBs) and higher socio-economic groups that does not stand up to scrutiny. No new evidence of a link between testicular cancer and POPs is presented in this paper. The authors state that PCBs and testicular cancer are ‘directly linked’. The authors cite two small studies which show a weak positive association between testicular cancer and PCBs. A recent, large and well-designed case–control study shows an inverse association between testicular cancer and several individual and grouped PCBs [2]. A more comprehensive synthesis of the total body of evidence is needed. They state ‘there does certainly seem to be a link with higher socio-economic status’. An aggregate of electoral districts in Cork with higher socio-economic status (SES) may have a greater incidence of testicular cancer, but this does not mean that testicular cancer is occurring at a greater frequency in men in higher socio-economic groups. SES was not recorded for individual men who had testicular cancer in this study. This is potential ecological bias [3]. The socio-economic status of cases is not collected by the National Cancer Registry of Ireland (NCRI). This is important when cancer rates for a small area are published. The socio-economic composition of a small area may be different from that of the comparison areas. Many specific cancers are linked to both socio-economic group and other known causes of cancer (smoking for instance). The confounding effect of social class on cancer, particularly in small areas, should always be considered before hypothesising a novel carcinogen. Worldwide, there is a strong public perception that environmental exposures are directly responsible for cancer. This is seldom the case. The epidemiological criteria for successful investigation of cancer clusters are a high relative risk (between 10 and 20); a rare cancer; the purported causative agent can be reliably measured in the environment; bio-monitoring is possible; there is heterogeneity of exposure in an area and a plausible route of exposure can be assessed [4]. These conditions are often not met, and most of them are not present in this study. However, the epidemiology may not matter as much as we think [5]. The strategic learning from the vast literature on cancer clusters is that regardless of the quality and validity of epidemiological and environmental investigation, if there has not been early and effective communication with the public, the scientific approach will not satisfy [6]. Publishing cancer rates without a comprehensive communication and investigation plan is not advised. This paper may cause anxiety, while it offers no plan of action and ignores the necessity of dealing with the community’s risk perception. Ireland needs a dedicated multi-disciplinary environment and health unit, with epidemiological, environmental and Public Health expertise. This unit could then respond to possible cancer clusters and other community environment and health concerns in a timely, coordinated, U. B. Fallon (&) Department of Public Health Medicine, HSE Dublin Mid-Leinster, Tullamore, Co. Offaly, Ireland e-mail: unab.fallon@hse.ie