Clusters and clustering of childhood cancer: A review

Methodological considerations in the study of clusters and clustering of ch ildhood cancer are reviewed briefly. A selection of 11 studies of individua l clusters of childhood leukaemia which are either particularly notable or recent and have been reported in peer review journals is then considered. F ocus is placed on sources of alerts, descriptive studies, field-work studie s, conclusions and communication management. Some of these studies are prob ably essential but they are unlikely to yield firm conclusions; studies of large data sets are recommended. No causal factor has been identified which can explain a single cluster of childhood leukaemia.