Patients undergo blood and urine collection prior to, periodically during, and after treatment with dactinomycin and vincristine for pharmacokinetic, pharmacodynamic, and pharmacogenetic analysis. Samples are analyzed using a liquid chromatography-tandem mass spectrometry assay. Genomic DNA extracted from peripheral blood mononuclear cells is isolated and analyzed by polymerase chain reaction and genotyping assays for genetic variation in genes relevant to the pharmacology of dactinomycin and vincristine.