Critical assessment of opposing views on trends in childhood cancer

Two articles reaching opposite conclusions on the current trends in childhood cancer have recently appeared in the literature. One concluded that pediatric cancers have increased dramatically, suggesting an effect from environmental hazards; the other concluded that rates for the major pediatric cancers have remained fairly stable, except for modest increases due to improvements in diagnosis or reporting. This review discusses the reasons for this discrepancy, including differences in the populations, age groups, and time periods analyzed. The arguments in favor of an increase are examined and shown to provide no convincing evidence that environmental pollutants have increased pediatric cancer rates over the past 20 to 30 years. Any suggested increase appears to be the result of non-causal factors, such as selective analysis and reporting, residual confounding by age, random variation, and stepwise improvements in diagnosis and classification.