Ondrej Blaha, PhD
Associate Research Scientist in BiostatisticsCards
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Featured Publications
Perioperative Modified FOLFIRINOX for Resectable Pancreatic Cancer
Cecchini M, Salem R, Robert M, Czerniak S, Blaha O, Zelterman D, Rajaei M, Townsend J, Cai G, Chowdhury S, Yugawa D, Tseng R, Arbelaez C, Jiao J, Shroyer K, Thumar J, Kortmansky J, Zaheer W, Fischbach N, Persico J, Stein S, Khan S, Cha C, Billingsley K, Kunstman J, Johung K, Wiess C, Muzumdar M, Spickard E, Aushev V, Laliotis G, Jurdi A, Liu M, Escobar-Hoyos L, Lacy J. Perioperative Modified FOLFIRINOX for Resectable Pancreatic Cancer. JAMA Oncology 2024, 10: 1027-1035. PMID: 38900452, PMCID: PMC11190830, DOI: 10.1001/jamaoncol.2024.1575.Peer-Reviewed Original ResearchProgression-free survivalPancreatic ductal adenocarcinomaOverall survivalCtDNA levelsPhase 2 nonrandomized controlled trialAnalysis of circulating tumor DNAMedian progression-free survivalResectable pancreatic ductal adenocarcinomaControlled trialsAssess surgical candidacyBaseline ctDNA levelModified 5-fluorouracilResectable pancreatic cancerPancreatic protocol computed tomographyAssociated with recurrenceTumor molecular featuresAggressive malignant tumorKaplan-Meier estimatesRandomized clinical trialsStandard of careCtDNA-positivePreoperative cyclesNonrandomized controlled trialsUnresectable diseaseModified FOLFIRINOXDesign and analysis of cluster randomized trials with time‐to‐event outcomes under the additive hazards mixed model
Blaha O, Esserman D, Li F. Design and analysis of cluster randomized trials with time‐to‐event outcomes under the additive hazards mixed model. Statistics In Medicine 2022, 41: 4860-4885. PMID: 35908796, PMCID: PMC9588628, DOI: 10.1002/sim.9541.Peer-Reviewed Original ResearchConceptsSample size formulaCluster sizeNew sample size formulaSample size proceduresSize formulaEffect parametersSandwich variance estimatorStatistical inferenceCluster size variationEvent outcomesRandomization-based testsImproved inferenceSize proceduresTreatment effect parametersVariance estimatorSmall sample biasesAnalysis of clustersSimulation studyUnequal cluster sizesFrailty termVariance inflation factorFailure timeSample size requirementsMixed modelsAppropriate definitionBayesian local exchangeability design for phase II basket trials
Liu Y, Kane M, Esserman D, Blaha O, Zelterman D, Wei W. Bayesian local exchangeability design for phase II basket trials. Statistics In Medicine 2022, 41: 4367-4384. PMID: 35777367, PMCID: PMC10279458, DOI: 10.1002/sim.9514.Peer-Reviewed Original Research
2025
Statistical considerations for evaluating treatment effect under various non-proportional hazard scenarios.
Zhang X, Greene E, Blaha O, Wei W. Statistical considerations for evaluating treatment effect under various non-proportional hazard scenarios. Statistical Methods In Medical Research 2025, 9622802241313297. PMID: 39930911, DOI: 10.1177/09622802241313297.Peer-Reviewed Original ResearchNon-proportional hazardsType I error rateAnalysis of time-to-event outcomesTime-to-event outcomesComparison of statistical methodsGeneralized gamma modelMaxCombo testGamma modelF modelOverall treatment effectTreatment effectsReal dataSurvival probabilityGeneralizationOncology trialsPublished oncology trials
2024
Distributions and Their Approximations for p-Values
Zhou, N., Blaha, O., Zelterman, D. (2024). Distributions and Their Approximations for p-Values. In: Chen, DG. (eds) Biostatistics in Biopharmaceutical Research and Development. Springer, Cham. https://doi.org/10.1007/978-3-031-65937-9_16ChaptersDistributions and Their Approximations for p-Values
Zhou N, Blaha O, Zelterman D. Distributions and Their Approximations for p-Values. 2024, 481-509. DOI: 10.1007/978-3-031-65937-9_16.Peer-Reviewed Original ResearchDistribution of p-valuesStudent-t distributionTesting multiple hypothesesT-distributionAlternative distributionsIdentified hypothesisSimulation studySignificant hypothesesDependent samplesApproximationAlternative hypothesisP-valueLack of independenceMultiple hypothesesExamplesIterationMultiplicationDistributionEstimationGlobal Disparities in the Characteristics and Outcomes of Leukemia Clinical Trials: A Cross-Sectional Study of the ClinicalTrials.gov Database.
Alhajahjeh A, Rotter L, Stempel J, Grimshaw A, Bewersdorf J, Blaha O, Kewan T, Podoltsev N, Shallis R, Mendez L, Stahl M, Zeidan A. Global Disparities in the Characteristics and Outcomes of Leukemia Clinical Trials: A Cross-Sectional Study of the ClinicalTrials.gov Database. JCO Global Oncology 2024, 10: e2400316. PMID: 39621951, DOI: 10.1200/go-24-00316.Peer-Reviewed Original ResearchAnalyzing determinants of premature trial discontinuation in leukemia clinical trials
Rotter L, Alhajahjeh A, Stempel J, Grimshaw A, Bewersdorf J, Blaha O, Kewan T, Podoltsev N, Shallis R, Mendez L, Stahl M, Zeidan A. Analyzing determinants of premature trial discontinuation in leukemia clinical trials. Leukemia & Lymphoma 2024, 66: 289-297. PMID: 39440622, DOI: 10.1080/10428194.2024.2416565.Peer-Reviewed Original ResearchClinical trialsSlow accrualLeukemia trialsEarly-phase trialsNon-randomized trialsAcademic-sponsored trialsImprove patient outcomesLeukemia clinical trialsSingle-centerTrial discontinuationSponsored trialsSmall trialsLeukemiaEarly terminationPatient outcomesLate-phaseIndependent reviewersTermination ratesComprehensive searchTrialsA Bayesian platform trial design with hybrid control based on multisource exchangeability modelling
Wei W, Blaha O, Esserman D, Zelterman D, Kane M, Liu R, Lin J. A Bayesian platform trial design with hybrid control based on multisource exchangeability modelling. Statistics In Medicine 2024, 43: 2439-2451. PMID: 38594809, PMCID: PMC11325877, DOI: 10.1002/sim.10077.Peer-Reviewed Original Research
2023
Validation of the Molecular International Prognostic Scoring System (IPSS-M) in Patients (Pts) with Myelodysplastic Syndromes/Neoplasms (MDS) Who Were Treated with Hypomethylating Agents (HMA)
Kewan T, Bewersdorf J, Blaha O, Stahl M, Al Ali N, DeZern A, Sekeres M, Carraway H, Desai P, Griffiths E, Stein E, Brunner A, Amaya M, Zeidner J, Savona M, Stempel J, Chandhok N, Logothetis C, Ramaswamy R, Rose A, Roboz G, Rolles B, Wang E, Harris A, Shallis R, Xie Z, Padron E, Maciejewski J, Sallman D, Della Porta M, Komrokji R, Zeidan A. Validation of the Molecular International Prognostic Scoring System (IPSS-M) in Patients (Pts) with Myelodysplastic Syndromes/Neoplasms (MDS) Who Were Treated with Hypomethylating Agents (HMA). Blood 2023, 142: 3240. DOI: 10.1182/blood-2023-186340.Peer-Reviewed Original ResearchComplete remission rateOverall response rateOutcome of ptsMedian overall survivalOverall survivalHypomethylating agentHMA initiationHR-MDSC-indexRisk groupsScoring systemInternational Prognostic Scoring SystemResponse criteriaPrognostic scoring systemHigh-risk diseaseLarge multicenter cohortHigh-risk groupHarrell's C-indexLog-rank testPrediction of outcomeDifferent scoring systemsSubsequent validation studiesHMA cyclesMedian followAllogeneic HSCT
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