Critical assessment of opposing views on trends in childhood cancer

Two articles reaching opposite conclusions on the current trends in childho od cancer have recently appeared in the literature. One concluded that pedi atric cancers have increased dramatically, suggesting an effect from enviro nmental hazards; the other concluded that rates for the major pediatric can cers have remained fairly stable, except for modest increases due to improv ements in diagnosis or reporting. This review discusses the reasons for thi s discrepancy, including differences in the populations, age groups, and ti me 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 suggest ed increase appears to be the result of non-causal factors, such as selecti ve analysis and reporting, residual confounding by age, random variation, a nd stepwise improvements in diagnosis and classification.