Geographical and ecological analyses of childhood acute leukaemias and lymphomas in north-west England.

Childhood leukaemias and lymphomas have been associated with exposure to environmental factors, including infections, which show geographical variation. This study examined the geographical distribution of the incidence of acute leukaemia and lymphoma using Manchester Children's Tumour Registry (MCTR) data 1976-2000. A total of 910 children were included, all of whom had histologically and/or cytologically verified leukaemia or lymphoma. At the time of their diagnoses, all the children were aged 0-14 years and were resident in the counties of Greater Manchester or Lancashire. Standardized morbidity ratios were calculated. Poisson regression was used to examine the relationship between incidence rates and small-area (census ward) population density, ethnic composition and deprivation index. There was a monotonic relationship between acute lymphoblastic leukaemia (ALL) incidence and population density (P = 0.05). Higher rates were seen in more densely populated areas. There was evidence for a monotonic relationship between the incidence of the mixed cellularity subtype of Hodgkin's disease (HD) and the Townsend deprivation score (P = 0.001). Markedly higher incidence was associated with greater levels of unemployment and household overcrowding. The results for ALL and mixed cellularity HD support the involvement of environmental factors, such as infections, in disease aetiology.

Geographical and ecological analyses of childhood Wilms' tumours and soft-tissue sarcomas in North West England.

The aim of this paper was to study the geographical distribution of Wilms' tumours (WT) and soft-tissue sarcomas (STS) for 0-14 year olds included in a population-based registry from North West England during 1976-2000. Standardised morbidity ratios (SMRs) were calculated. Relationships between incidence rates and small area (ward) population density, ethnic composition, deprivation index and urban-rural status were examined using Poisson regression. There was a non-linear relationship between WT incidence and population density (P=0.008), with a higher incidence associated with wards with low deprivation scores (P=0.02); and which included a greater proportion of whites (P=0.01). For STS, a higher incidence was associated with wards with low deprivation scores (P=0.04); and which were 'more rural/less urban' (P=0.03). These results are consistent with a role for localised environmental exposures, in combination with lifestyle factors, in the aetiology of WT. For STS, there is some evidence for the involvement of environmental and/or lifestyle factors.

Space-time clustering patterns in childhood solid tumours other than central nervous system tumours.

The aetiology of most childhood solid tumours (other than central nervous system [CNS] tumours) is unclear. To investigate whether certain environmental exposures may be involved, we have analysed for space-time clustering using population-based data from North West England for the period 1954-98. Knox tests for space-time interactions between cases were applied with fixed thresholds of close in space, <5 km, and close in time, <1 year apart. Addresses at birth and at diagnosis were used. Tests were repeated replacing geographical distance with distance to the Nth nearest neighbour. N was chosen such that the mean distance was 5 km. Data were also examined by a second order procedure based on K-functions. There was significant evidence of space-time clustering for Wilms' tumours (p = 0.03 and 0.04, using the geographical distance and nearest neighbour versions of the Knox test; and p = 0.07 and 0.03, using the geographical distance and nearest neighbour versions of the K-function method), and soft tissue sarcomas (p = 0.01, using both the geographical distance and nearest neighbour versions of the Knox test; and p = 0.001 and 0.002, using the geographical distance and nearest neighbour versions of the K-function method) based on time and location at birth, but not time and location at diagnosis. There was little or no evidence of space-time clustering amongst other diagnostic groups. These are the first results to demonstrate space-time clustering for childhood Wilms' tumours and soft tissue sarcomas. The results are consistent with environmental exposure hypotheses, relating to locations pre-natally or peri-natally.