Cancer Cluster Investigations: Review of the Past and Proposals for the Future

Abstract

Residential clusters of non-communicable diseases are a source of enduring public concern, and at times, controversy. Many clusters reported to public health agencies by concerned citizens are accompanied by expectations that investigations will uncover a cause of disease. While goals, methods and conclusions of cluster studies are debated in the scientific literature and popular press, investigations of reported residential clusters rarely provide definitive answers about disease etiology. Further, it is inherently difficult to study a cluster for diseases with complex etiology and long latency (e.g., most cancers). Regardless, cluster investigations remain an important function of local, state and federal public health agencies. Challenges limiting the ability of cluster investigations to uncover causes for disease include the need to consider long latency, low statistical power of most analyses, uncertain definitions of cluster boundaries and population of interest, and in- and out-migration. A multi-disciplinary Workshop was held to discuss innovative and/or under-explored approaches to investigate cancer clusters. Several potentially fruitful paths forward are described, including modern methods of reconstructing residential history, improved approaches to analyzing spatial data, improved utilization of electronic data sources, advances using biomarkers of carcinogenesis, novel concepts for grouping cases, investigations of infectious etiology of cancer, and “omics” approaches.

A spatial analysis of childhood cancer and industrial air pollution in a metropolitan area of Colombia

“…The main strength of this study is the quality of the CC data and the period of 16 years included for the analysis. The cancer registries are considered the best source of information to measure cancer burden in a given time and region 15,47 . The BMA cancer registry is considered high quality by IARC due to the integrity, punctuality, and accuracy of the data provided, which translates into highly standardized and reliable data.…”

“…The International Agency for Research on Cancer (IARC) established in 2013 that there was sufficient evidence about the carcinogenicity of outdoor air pollution, specifically of fine particulate matter (PM 2.5 ) 12 . Studies conducted in Europe and North America have found an association between CC and proximity to industrial sources that emit pollutants into the air 5,9,10,13,14 ; also, since the beginning of the 20th century, geographic clusters of cancer have been identified, mainly for leukemia 15 . The mixture of pollutants varies widely in space and time, reflecting the heterogeneity of their sources, the influence of climate, atmospheric transformations, and other factors, and therefore health effects might also differ widely in space and time and cannot be generalized.…”

A spatial analysis of childhood cancer and industrial air pollution in a metropolitan area of Colombia

“…The main strength of this study is the quality of the CC data and the period of 16 years included for the analysis. The cancer registries are considered the best source of information to measure cancer burden in a given time and region [15] [51], the RPC-AMB is considered high quality by IARC due to the integrity, punctuality and accuracy of the data provided, which translates into highly standardized and reliable data. Therefore, the classification of the disease is considered adequate for the cases included in the analyzes performed.…”

“…During 2013, the International Agency for Research on Cancer (IARC) found that there is sufficient evidence about the carcinogenicity of outdoor air pollution in general and fine particulate matter (PM 2,5 ) [12]. Research published in Europe and North America, have found association between CC and proximity to industrial sources that emit pollutants into the air [5][9][10][13][14]; also, since the beginning of the 20th century, geographic clusters of cancer have been identified, mainly for leukemia [15]. The mixture of pollutants varies widely in space and time, reflecting the heterogeneity of their sources, the influence of climate, atmospheric transformations, and other factors, and therefore health effects might also differ widely in space and time and cannot be generalized.…”

Childhood cancer in small geographical areas and proximity to air-polluting industries

“…In the literature, there are very few studies of cluster of cases of lymphomas in children. A British space-time clustering study found space-time clustering for HL and NHL (Goodman et al, 2014). Proximity to high-capacity thoroughfares has also been associated with the incidence of NHL among Danish children (Raaschou-Nielsen et al, 2001).…”