There is a public health need to balance timely generation of hypotheses with cautious causal inference. For rare cancers this is particularly challenging because standard epidemiological study designs may not be able to elucidate causal factors in an early period of emerging risks.

We have previously demonstrated that open-access databases (the GLOBOCAN 2008 resource combined with data from the United Nations Development Report and the World Bank list of Development Indicators) can be used to explore associations between potential risk factors and incidence of cancer of the brain and central nervous system at an ecological level (publication in press).

In this study we showed that the only exogenous risk factor consistently associated with higher incidence rates of cancer of the brain and central nervous system was the penetration rate of mobile/cellular telecommunications subscriptions. Furthermore, this approach enabled evaluation of latency periods between exposure and clinical onset of the disease. For most cancers this is difficult to evaluate using standard epidemiological study designs, but this work showed that this latency period is at least 11−12 years, but probably more than 20 years.

These results showed that readily available ecological data may be underused, particularly for the study of risk factors for rare diseases and those with long latencies.

Because these analyses were done using a systematic, a priori set out statistical approach, it can be extended to other combinations of diseases and exogenous risk factors. In addition to demonstrating the methodology for cancers of the brain and central nervous system, we will show results evaluating associations between the incidence of other (rare) cancers and potential risk factors from the World Bank list of Development Indicators.