Summary The European Childhood Leukaemia-Lymphoma Incidence Study (ECLIS) is designed to address concerns about a possible increase in the risk of cancer in Europe following the nuclear accident in Chernobyl in 1986. This paper reports results of surveillance of childhood leukaemia in cancer registry populations from 1980 up to the end of 1991. There was a slight increase in the incidence of childhood leukaemia in Europe during this period, but the overall geographical pattern of change bears no relation to estimated exposure to radiation resulting from the accident. We conclude that at this stage of follow-up any changes in incidence consequent upon the Chernobyl accident remain undetectable against the usual background rates. Our results are consistent with current estimates of the leukaemogenic risk of radiation exposure, which, outside the immediate vicinity of the accident, was small.

Summary The interpretation of reports of clusters of childhood leukaemia is difficult, first because little is known about the causes of the disease, and second because there is insufficient information on whether cases show a generalized tendency to cluster geographically. The EUROCLUS project is a European collaborative study whose primary objective is to determine whether the residence locations of cases at diagnosis show a general tendency towards spatial clustering. The second objective is to interpret any patterns observed and, in particular, to see if clustering can be explained in terms of either infectious agents or environmental hazards as aetiological agents. The spatial distribution of 13 351 cases of childhood leukaemia diagnosed in 17 countries between 1980 and 1989 has been analysed using the Potthoff-Whittinghill method. The overall results show statistically significant evidence of clustering of total childhood leukaemia within small census areas (P= 0.03) but the magnitude of the clustering is small (extra-Poisson component of variance (%) = 1.7 with 90% confidence interval 0.2-3.1). The clustering is most marked in areas that have intermediate population density (150-499 persons km-2). It cannot be attributed to any specific age group at diagnosis or cell type and involves spatial aggregation of cases of different ages and cell types. The results indicate that intense clusters are a rare phenomenon that merit careful investigation, although aetiological insights are more likely to come from investigation of large numbers of cases. We present a method for detecting clustering that is simple and readily available to cancer registries and similar groups.

Summary The EUROCLUS project included information on residence at diagnosis for 13 351 cases of childhood leukaemia diagnosed in the period 1980-89 in defined geographical regions in 17 countries. A formal algorithm permits identification of small census areas as containing case excesses. The present analysis examines spatial-temporal patterns of the cases (n = 970) within these clustered areas. The objectives were, first, to compare these results with those from an analysis conducted for UK data for the period 1966-83, and, second, to extend them to consider infant leukaemias. A modification of the Knox test investigates, within the small areas, temporal overlap between cases in a subgroup of interest at a putative critical time and all other cases at any time between birth and diagnosis. Critical times were specified in advance as follows: for cases of acute lymphoblastic leukaemia aged 2-4 years, the 18-month period preceding diagnosis; for cases of total leukaemia aged 5-14 years, 1 year before to 1 year after birth; and for infant cases (diagnosed < 1 year), 1 year before to 6 months after birth. Each of the analyses found evidence of excess space-time overlap compared with that expected; these were 10% (P = 0.005), 15% (P = 0.0002) and 26% (P = 0.03) respectively. The results are interpreted in terms of an infectious origin of childhood leukaemia.Keywords: infection; childhood leukaemia; acute lymphoblastic leukaemia; delayed exposure; infant leukaemia; in utero exposure; cluster Leukaemia is the most frequent childhood malignancy (Parkin et al, 1988), but the cause of the majority of cases remains unknown (Doll, 1989). Reports of clusters of leukaemia, usually involving children, have been frequent throughout this century (Alexander, 1993), but their aetiological significance remains obscure. The EUROCLUS project was established to investigate the geographical pattern of the disease using specialist registry data from a wide spectrum of European countries, and also from Queensland, Australia. The primary objective was to determine whether the disease showed a general tendency to cluster within small areas. The results (Alexander et al, 1998) show statistically significant evidence of clustering, although the magnitude is small. The only previous investigation of spatial clustering of childhood leukaemia (CL) in a large dataset was conducted in the UK (Draper, 1990 (1993) and Kinlen (1995). A second objective of EUROCLUS was to test these hypotheses and make comparisons with the results of the UK analysis (Alexander, 1992). Specific subgroups of interest are (a) cases of acute lymphoblastic leukaemia (ALL) in the childhood peak, and (b) cases of CL aged 5-14 years. Critical times, specified in advance are for (a) the 18-month period preceding diagnosis, and for (b), 1 year before to 1 year after birth.A third subgroup of interest that had not been included in the UK analysis is infant leukaemia (diagnosed < 1 year or < 18 months), which has recently emerged as an interesting biological entity as a large...

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Summary Data from the Registry of Digestive tumours of the D6partement of Cote d'Or (France) were used to study the characteristics of gastrointestinal non-Hodgkin's lymphomas in the 1976-90 period. The mean annual age-standardized incidence rate was 0.94 per 100 000 for men, and 0.54 per 100 000 for women. Incidence varied little during the study period. Overall 5-year survival rate was 34.3 ± 5.6%.