Infectious proxies and childhood leukaemia: findings from the United Kingdom Childhood Cancer Study (UKCCS).

The United Kingdom Childhood Cancer Study (UKCCS) was specifically designed to investigate the potential etiological role of infections as one of its objectives and information on a number of markers of infectious exposure from multiple sources was collected (www.ukccs.org). This study found that a mother's recollections of past minor illness episodes in her children were unreliable, producing systematic case-control differences. From birth onwards children diagnosed with ALL between 2-5 years were found to have had more clinically diagnosed infectious illness episodes (not fewer) than unaffected children, with those with two or more neonatal infections being diagnosed with leukaemia around 7 months earlier than those with only one or none. The findings from these analyses and their implications for future research are reviewed and discussed in this paper.