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Previously, we identified space-time clustering in certain childhood cancers around diagnosis residence. These findings provided support for the involvement of environmental agents in etiological processes occurring close to diagnosis. We have reanalyzed the same British population-based dataset. The aim of the study was to determine whether there was space-time clustering around the residence at birth in relation to time of birth and separately from time of diagnosis. A total of 29,553 cases, diagnosed during the period 1969-1993, were examined by a second-order procedure based on K-functions. Locations were birth addresses, but separately, both dates of birth and diagnosis were analyzed. There was statistically significant space-time clustering for Hodgkin lymphoma (HL) and central nervous system (CNS) tumors (p=0.047 and 0.01, respectively, based on birth date) and for total leukemia at ages 1-4 years only, Non-Hodgkin lymphoma (NHL) and Wilms tumor (p=0.01, 0.02 and 0.006, respectively, based on diagnosis date). These results, interpreted together with other epidemiological evidence, suggest an etiological role for environmental factors focused around birth address for certain childhood cancers. For HL and CNS tumors, findings suggest that etiological exposures occurred at similar ages or in utero. For leukemia, NHL and Wilms tumor there is support for exposures occurring at similar times before diagnosis. For leukemia, HL, NHL and CNS tumors, but not Wilms tumor, the findings are consistent with infectious hypotheses., (Copyright (c) 2008 Wiley-Liss, Inc.)

Previous studies have provided evidence that infections may play a part in the aetiology of certain childhood cancers. The finding of space-time clustering indicates the presence of an environmental component to aetiology and is especially supportive of a role for infections. Space-time clustering occurs when excess numbers of cases of a disease are observed within small geographical locations at limited periods of time and this cannot be explained in terms of general excesses in those locations or at those times. To investigate whether infections may be involved in the aetiology of childhood cancer, we have analysed for space-time clustering using a large set of national population-based data from Great Britain for the period 1969-1993. Data were examined by a second-order procedure based on K-functions, with fixed thresholds of closeness in space (0.5-7.5 km) and closeness in time (0.1-1.5 years). Locations were addresses at diagnosis. Tests were repeated, replacing geographical distances with distances to the 19th-33rd nearest neighbours and this provided the primary result for each analysis. There were a total of 32,295 cases of childhood cancer. The analyses showed statistically significant evidence of space-time clustering for acute lymphoblastic leukaemia over the whole age range (p = 0.04), but especially for ages 1-4 years (p = 0.03). There was less statistically significant evidence for total leukaemia (p = 0.048). Significant space-time clustering was also evident for soft tissue sarcomas (p = 0.03) and osteosarcomas (p = 0.02). Results support other evidence suggesting a role for infections in the aetiology of these particular diagnostic groups.