The influence of subsequent neoplasms on incidence trends in childhood cancer.

The purpose of this analysis was to evaluate to what extent subsequent malignant neoplasms account for the increasing rates of cancer occurrence among children. Data from the population-based Surveillance, Epidemiology, and End Results program were used to calculate age-standardized annual incidence rates from 1974-1989 for 10 common cancers among children 14 years of age or younger. Mean rates and linear trends were evaluated using least squares regression, first for all neoplasms and then excluding subsequent neoplasms, to determine if the removal of subsequent neoplasms would attenuate increasing trends. Increasing annual incidence rates were found for all childhood cancers combined, acute lymphoid leukemia, and brain tumors, but not for other cancer types. Excluding subsequent neoplasms from the analysis had a negligible effect on the trends we observed. Although it remains largely undetermined why childhood cancer incidence rates are increasing in the United States, this study presents evidence that subsequent primary neoplasms do not substantively contribute to these observed trends.