MethotrexateHarm ReductionPolyglutamic AcidAntirheumatic AgentsFolic Acid AntagonistsTetrahydrofolate DehydrogenaseArthritis, RheumatoidAminopterinAntimetabolites, AntineoplasticLeukemia L1210Reduced Folate Carrier ProteinTrimetrexateFolic AcidDrug Therapy, Combinationgamma-Glutamyl HydrolaseLeucovorinTetrahydrofolatesTreatment OutcomeAbortifacient Agents, NonsteroidalCyclophosphamideDrug ResistanceAntineoplastic Combined Chemotherapy ProtocolsImmunosuppressive AgentsSulfasalazineDrug Administration ScheduleVincristineDeoxyuridinePrecursor Cell Lymphoblastic Leukemia-Lymphoma6-MercaptopurineDermatologic AgentsPregnancy, EctopicFluorouracilFormyltetrahydrofolatesFolate Receptors, GPI-AnchoredDoxorubicinPhosphoribosylaminoimidazolecarboxamide FormyltransferaseDose-Response Relationship, DrugOsteosarcomaInjections, SpinalPrednisoneCytarabineThymidylate SynthaseLeukemia, LymphoidHydroxychloroquineCentral Nervous System NeoplasmsPregnancy, TubalSarcoma 180Pteroylpolyglutamic AcidsIsoxazolesPsoriasisAsparaginaseGestational Trophoblastic DiseaseRemission InductionBiological TransportHydroxymethyl and Formyl TransferasesProbenecidTime FactorsMucositisDouble-Blind MethodNucleotide DeaminasesCarcinoma, Ehrlich TumorCombined Modality TherapyVinblastineAntibodies, MonoclonalArthritis, JuvenileArthritis, PsoriaticAdministration, OralSelf-Injurious BehaviorTrophoblastic NeoplasmsBreast NeoplasmsLeukemia L5178Severity of Illness IndexCisplatinSurvival AnalysisHypoxanthines