April 12, 2017

expert reaction to IARC audit of worldwide childhood cancer incidence

The International Agency for Research on Cancer (IARC) has published it’s audit of worldwide childhood cancer rates in the Lancet Oncology.

Prof. Mel Greaves, Director of the Centre for Evolution and Cancer at The Institute of Cancer Research, London, said:

“The IARC audit of worldwide incidence rates of childhood cancers is much welcomed and will provide a firm foundation for exploring causation.

“The prime position of leukaemia in the list is to be expected from prior data from IARC and elsewhere. The 13 per cent increase in overall rate over 20 years is intriguing. We know from previously published data that the major subtype of childhood cancer – acute lymphoblastic leukaemia, or ALL, has been increasing at a steady rate of around 1 per cent per year in Western Europe since at least the early 1980s. Other leukaemias have a lower rate of increase or no increase. The increased incidence of ALL cannot be ascribed to changes in inherited genetics or better diagnosis. Many possible causes of ALL have been suggested including ionising and non-ionising radiation and chemical pollution but there is no robust evidence for this.

“Childhood ALL has its highest incidence in the most affluent societies. The most plausible explanation for the increase in ALL is that it reflects changing patterns of microbial exposure early in life, such as in infancy. The immune system of new-borns requires benign exposure to infection to prime its complex network for subsequent appropriate responses. Modern societies with decreased social contacts and more efficient hygiene have muted these exposures. In the absence of this early immunological experience, subsequent responses are abnormal and may trigger ALL in susceptible individuals. A similar explanation has been offered for the increases in childhood allergies and type 1 diabetes that, like ALL, track generally with affluence. The explanation may therefore be a paradox of progress.”

Prof. Richard Peto, professor of medical statistics at the University of Oxford, said:
“It is wrong to claim that real childhood cancer rates are increasing worldwide. Since the 1980s, medical services and diagnostic methods have improved, as has  the thoroughness with which cancers get reported to population-wide cancer registries. These improvements could well explain the 13% increase since the 1980s in the proportion of children reported to develop cancer.”

“The Lancet Oncology report [11 April 2017] of a 13% increase in global childhood cancer rates includes many statements by the authors emphasising the uncertainties in assessing time trends, which are reflected in the first paragraph of the IARC press release, yet these cautions inevitably get ignored in the headline of the press release.”

Declared interests
None declared.