What are cancer clusters?
A cancer cluster can be defined as a greater than expected number of cancer cases occurring within a group of people living in a particular geographical area over a specific time period. The complex patterns of occurrence of cancer make it difficult to identify and interpret cancer clusters. All types of cancer can occur in clusters by chance for purely statistical reasons; this type of clustering occurs when the incidence of cancer is not affected by any external factors, or when there are external factors causing cancer but they are ubiquitous among the population. There are statistical approaches that enable the recognition of clustering which is over and above that due to chance, ie, that make it possible to determine whether clusters exist that are due to the localised influence of a risk factor. This type of approach was used in COMARE’s 11th Report of the distribution of childhood cancer in Britain that is being carried out with particular reference to concerns about possible cl
