Progress resulting from clinical trials. Solid tumors in childhood cancer.

Solid tumors account for approximately 70% of malignant neoplasms in children younger than 15 years of age. The 5-year survival of children with solid tumors increased from 27% to 70% between 1960 and 1990. The slope of the curve that describes the change in survival over this period is remarkably constant, reflecting the nature of progress made through clinical trials. In addition to providing data important for the refinement of treatment for specific tumors, clinical trials have made numerous important, global contributions for the practice of oncology. The development of uniform response criteria, for example, was necessitated by clinical trials. The identification of histologic subtypes and the recognition of prognostic variables have permitted refinements in diagnosis and staging. By exploring novel strategies for the integration of different therapeutic modalities, clinical trials have identified indications for the use of presurgical chemotherapy, preradiation chemotherapy, and second-look and delayed primary surgeries. Refinements in the utilization of chemotherapy have been made possible by the evaluation of new agents, the study of dose intensity, and the use of the "window of opportunity" to identify active agents for tumors for which there is no effective treatment. Clinical trials have been instrumental in defining the late effects of treatment, investigating the causes of childhood cancer through epidemiologic studies, and supporting cancer biology research. The close collaboration of basic and clinical investigators offers the best opportunity for realizing the rewards of transitional research.