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  string(146) "Heterogeneity of Clinical Benefit from Erdafitinib in FGFR3-Altered Urothelial Carcinoma: A Post Hoc Subgroup Analysis of the Phase III THOR Trial"
  ["project_narrative_summary"]=>
  string(772) "The phase III THOR trial showed a survival benefit of erdafitinib in FGFR3-altered advanced urothelial carcinoma after immune checkpoint inhibitor (ICI) therapy. Using YODA individual patient-level data, we will identify modifiers of erdafitinib efficacy in post hoc analyses. We will compare treatment benefit by FGFR3 alteration subtype (hotspot mutations vs fusion variants), by prior ICI exposure (agent, duration, response pattern), and by FGFR testing characteristics (central vs local; tissue vs blood; archival vs recent sampling). We will also explore whether early on-target toxicities of FGFR inhibition are associated with outcomes using bias-aware methods. Results will refine patient selection and guide sequencing of FGFR inhibition in urothelial carcinoma."
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    ["first_name"]=>
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    ["last_name"]=>
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    ["degree"]=>
    string(7) "MD, PhD"
    ["primary_affiliation"]=>
    string(54) "Kanazawa University Graduate School of Medical Science"
    ["email"]=>
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    string(8) "Ishikawa"
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  ["property_scientific_abstract"]=>
  string(1278) "Background
The phase III THOR trial demonstrated improved survival with erdafitinib compared with chemotherapy in patients with FGFR3-altered advanced urothelial carcinoma after immune checkpoint inhibitor (ICI) therapy. However, heterogeneity in FGFR3 alteration subtypes, prior ICI exposure, biomarker testing practices, and treatment-related toxicities has not been fully evaluated.
Objective
To identify molecular and clinical modifiers of erdafitinib efficacy using individual participant-level data from the THOR trial.
Study Design
Post hoc subgroup analyses of a randomized phase III trial.
Participants
Patients with advanced or metastatic urothelial carcinoma and confirmed FGFR3 alterations treated with erdafitinib or chemotherapy after prior ICI therapy.
Primary and Secondary Outcome Measures
Overall survival, progression-free survival and objective response rate (secondary), evaluated across FGFR3 alteration subtypes, prior ICI characteristics, FGFR testing methods, and early on-target toxicities.
Statistical Analysis
Kaplan–Meier methods and Cox proportional hazards models with interaction terms will be used. Landmark and sensitivity analyses will be performed as appropriate." ["project_brief_bg"]=> string(2600) "Background
Fibroblast growth factor receptor (FGFR) alterations define a molecularly distinct subset of urothelial carcinoma and represent an established therapeutic target. Erdafitinib, an oral pan-FGFR inhibitor, demonstrated a significant overall survival benefit over chemotherapy in the phase III THOR trial among patients with advanced urothelial carcinoma harboring FGFR3 alterations after immune checkpoint inhibitor (ICI) therapy. These results led to regulatory approval and incorporation of erdafitinib into treatment algorithms for FGFR-altered disease.
Despite this advance, FGFR3-altered urothelial carcinoma encompasses substantial biological and clinical heterogeneity. FGFR3 alterations include multiple activating point mutations and fusion variants, which may differ in oncogenic signaling, tumor biology, and therapeutic sensitivity. In addition, patients enrolled in THOR had heterogeneous prior ICI exposure, variable biomarker testing strategies (central versus local testing, tissue versus blood-based assays), and diverse treatment-related toxicity profiles. These sources of heterogeneity were not fully addressed in the primary trial analyses, leaving uncertainty regarding which patient subsets derive the greatest and most durable benefit from FGFR inhibition.
Project Significance
This project seeks to address these knowledge gaps through post hoc analyses of individual participant-level data from the THOR trial obtained via the YODA Project. By systematically evaluating molecular subtypes of FGFR3 alterations, prior ICI treatment characteristics, biomarker testing practices, and early on-target toxicities, this study aims to identify clinically meaningful modifiers of erdafitinib efficacy.
The significance of this work lies in its potential to refine patient selection and optimize treatment sequencing for FGFR-targeted therapy in urothelial carcinoma. Rather than treating FGFR3-altered disease as a binary entity, this study will provide a more nuanced framework for understanding variability in treatment benefit. Importantly, the findings are expected to be generalizable beyond the THOR trial, informing real-world clinical decision-making and the design of future clinical trials evaluating FGFR inhibitors or combination strategies.
By leveraging rigorously collected randomized trial data and applying bias-aware analytical approaches, this project will materially enhance scientific understanding of FGFR-driven urothelial carcinoma and contribute actionable insights to precision oncology and public health." ["project_specific_aims"]=> string(1542) "Specific Aims of the Project
The overall objective of this project is to identify molecular and clinical modifiers of treatment benefit from erdafitinib in patients with advanced urothelial carcinoma harboring FGFR3 alterations, using individual participant-level data from the phase III THOR trial.
Aim 1. To evaluate whether the efficacy of erdafitinib differs according to FGFR3 alteration subtype.
Hypothesis: Patients with activating FGFR3 point mutations and those with FGFR3 fusion variants derive differential clinical benefit from erdafitinib, reflecting biological heterogeneity within FGFR3-altered disease.
Aim 2. To assess the impact of prior immune checkpoint inhibitor (ICI) exposure on outcomes with erdafitinib.
Hypothesis: Characteristics of prior ICI therapy, including treatment duration and response patterns, modify subsequent survival outcomes following FGFR inhibition.
Exploratory Aim. To examine the influence of biomarker testing practices and treatment-related toxicities on erdafitinib efficacy.
Hypothesis: Variability in FGFR testing (central vs local testing, tissue vs blood-based assays, and timing of sample acquisition) and the early development of on-target toxicities are associated with differences in clinical outcomes.
Through these aims, this study seeks to move beyond a binary classification of FGFR3-altered urothelial carcinoma and provide a more refined framework for patient selection and therapeutic decision-making with FGFR inhibitors." ["project_study_design"]=> array(2) { ["value"]=> string(14) "indiv_trial_an" ["label"]=> string(25) "Individual trial analysis" } ["project_purposes"]=> array(3) { [0]=> array(2) { ["value"]=> string(56) "new_research_question_to_examine_treatment_effectiveness" ["label"]=> string(114) "New research question to examine treatment effectiveness on secondary endpoints and/or within subgroup populations" } [1]=> array(2) { ["value"]=> string(49) "new_research_question_to_examine_treatment_safety" ["label"]=> string(49) "New research question to examine treatment safety" } [2]=> array(2) { ["value"]=> string(76) "confirm_or_validate previously_conducted_research_on_treatment_effectiveness" ["label"]=> string(76) "Confirm or validate previously conducted research on treatment effectiveness" } } ["project_research_methods"]=> string(1488) "Data for this study will be obtained from the phase III THOR trial through the YODA Project. Only individual participant-level data from the THOR trial will be used. No data from external studies or other data sources will be included, and no data pooling or meta-analysis with non-YODA datasets is planned.
The study population will include all patients enrolled in the THOR trial who met the original trial eligibility criteria and were randomized to receive erdafitinib or investigator’s choice chemotherapy. Key inclusion criteria applied for this analysis are: adults with advanced or metastatic urothelial carcinoma; documented FGFR3 alterations as defined by the trial protocol; prior treatment with at least one immune checkpoint inhibitor; and availability of relevant baseline, treatment, and outcome data.
No additional exclusion criteria beyond those specified in the original THOR trial protocol will be applied. Patients will not be excluded on the basis of FGFR3 alteration subtype, prior immune checkpoint inhibitor characteristics, biomarker testing method (central or local), specimen type (tissue or blood), timing of sample acquisition, or treatment-related adverse events, as these factors constitute the primary variables of interest for the proposed subgroup analyses.
All analyses will be conducted using individual participant-level data within the secure YODA analysis environment, without aggregation of summary-level data across studies." ["project_main_outcome_measure"]=> string(1746) "Primary and Secondary Outcome Measures
The primary outcome measure for this study is overall survival (OS), defined as the time from randomization in the THOR trial to death from any cause. Patients alive at the time of data cutoff will be censored at the date of last known follow-up. OS was selected as the primary endpoint to ensure consistency with the primary endpoint of the THOR trial and to allow direct comparison with previously reported results.
Secondary outcome measures include progression-free survival (PFS) and objective response rate (ORR). PFS is defined as the time from randomization to radiographic disease progression or death from any cause, whichever occurs first, according to the criteria used in the original trial protocol. Patients without documented progression or death will be censored at the date of last disease assessment. ORR is defined as the proportion of patients achieving a complete or partial response, as assessed per trial-defined response criteria.
All outcome measures will be analyzed within clinically and biologically relevant subgroups, including FGFR3 alteration subtype (activating point mutations vs fusion variants), characteristics of prior immune checkpoint inhibitor therapy, biomarker testing methods (central vs local testing, tissue vs blood-based assays, and timing of sample acquisition), and the occurrence of early on-target treatment-related adverse events.
No changes to the definitions of the primary or secondary outcome measures are planned for the final analysis or publication. Outcomes will be reported using definitions consistent with the original THOR trial to ensure transparency, reproducibility, and comparability with existing literature." ["project_main_predictor_indep"]=> string(1335) "The primary independent variable is treatment assignment, defined as randomization to erdafitinib versus investigator’s choice chemotherapy in the THOR trial. Treatment assignment will be used as the main exposure variable for analyses of overall survival, progression-free survival, and objective response rate.
Key independent variables for effect modification analyses include FGFR3 alteration subtype, prior immune checkpoint inhibitor (ICI) exposure, FGFR biomarker testing characteristics, and treatment-related toxicities. FGFR3 alterations will be categorized as activating point mutations versus fusion variants. Prior ICI exposure will be defined by treatment duration and response pattern, and by ICI agent when available. FGFR testing will be categorized by testing source (central vs local), specimen type (tissue vs blood-based assays), and timing of sample acquisition (archival vs recent). Treatment-related adverse events will be evaluated in exploratory analyses, focusing on early on-target toxicities characteristic of FGFR inhibition, using clinically appropriate time windows to minimize bias.
All independent variables will be defined using data available in the THOR trial dataset and applied consistently across analyses to ensure reproducibility and comparability with final published results." ["project_other_variables_interest"]=> string(1459) "Additional variables will be used to characterize the study population and for multivariable risk adjustment in survival analyses. Demographic variables will include age at randomization (continuous) and sex (male vs female). Baseline clinical characteristics will include Eastern Cooperative Oncology Group (ECOG) performance status (0–1 vs 2), presence of visceral metastases (yes vs no), and primary tumor site.
Disease-related variables will include prior lines of systemic therapy (continuous and categorized as ≤2 vs >2), prior platinum-based chemotherapy (yes vs no), and time from initial diagnosis to randomization. When available, baseline laboratory or disease burden indicators reported in the trial dataset will be incorporated as covariates.
Treatment-related variables will include treatment arm (erdafitinib vs chemotherapy), chemotherapy type in the control arm (docetaxel vs vinflunine), starting dose of erdafitinib, dose modifications (yes vs no), and treatment duration. Geographic region, as defined in the original trial, will be included to account for potential regional differences.
All covariates will be defined using trial-reported data elements and categorized in alignment with the original THOR trial protocol where applicable. These variables will be included in multivariable Cox proportional hazards models to adjust for potential confounding and to ensure robust estimation of treatment effects." ["project_stat_analysis_plan"]=> string(3499) "All analyses will be conducted using individual participant-level data from the THOR trial within the secure YODA analysis environment. Statistical analyses will follow a predefined analysis plan and will be performed using standard statistical software.
Descriptive Analyses
Baseline demographic, clinical, molecular, and treatment-related characteristics will be summarized by treatment arm using appropriate descriptive statistics. Continuous variables will be reported as means with standard deviations or medians with interquartile ranges, as appropriate, and categorical variables as counts and percentages. Between-group comparisons will be performed using chi-square or Fisher’s exact tests for categorical variables and t-tests or non-parametric tests for continuous variables, as appropriate.
Primary and Secondary Outcome Analyses
Overall survival (OS) and progression-free survival (PFS) will be analyzed using the Kaplan–Meier method, with differences between treatment groups assessed using log-rank tests. Median survival times and survival rates at selected time points will be reported with corresponding confidence intervals. Cox proportional hazards regression models will be used to estimate hazard ratios and 95% confidence intervals.
Multivariable Cox models will be constructed to adjust for prespecified covariates, including age, sex, ECOG performance status, presence of visceral metastases, prior lines of therapy, geographic region, and treatment arm. Proportional hazards assumptions will be evaluated using standard diagnostic methods.
Objective response rate (ORR) will be compared between treatment groups using chi-square or Fisher’s exact tests, and effect estimates will be reported with corresponding confidence intervals.
Subgroup and Effect Modification Analyses
Prespecified subgroup analyses will be conducted to evaluate effect modification of treatment assignment across clinically relevant variables, including FGFR3 alteration subtype, prior immune checkpoint inhibitor (ICI) exposure characteristics, and FGFR biomarker testing features. Interaction terms between treatment assignment and subgroup variables will be included in Cox models to formally assess heterogeneity of treatment effects. Subgroup analyses will be interpreted as exploratory.
Analysis of Treatment-Related Toxicities
The association between early on-target treatment-related adverse events and clinical outcomes will be explored. To minimize time-dependent bias, landmark analyses will be performed at predefined time points, and sensitivity analyses using time-dependent covariates in Cox models will be conducted when appropriate.
Sensitivity Analyses
Sensitivity analyses will be performed to assess the robustness of findings, including analyses stratified by chemotherapy type in the control arm and by biomarker testing source (central vs local). Additional analyses excluding patients with missing key covariates may be conducted as appropriate.
Missing Data
Missing data will be described for all key variables. Primary analyses will be conducted using available-case data. When appropriate, sensitivity analyses will be performed to evaluate the potential impact of missing data on study findings.
All statistical tests will be two-sided, and results will be interpreted in the context of multiple exploratory analyses without formal adjustment for multiplicity." ["project_software_used"]=> array(1) { [0]=> array(2) { ["value"]=> string(7) "rstudio" ["label"]=> string(7) "RStudio" } } ["project_timeline"]=> string(1125) "The anticipated project start date is within one month of data access approval through the YODA Project, following completion of the Data Use Agreement and access setup.
During Months 1–2, data familiarization, data cleaning, and confirmation of variable definitions will be completed. Primary and secondary statistical analyses, including prespecified subgroup and sensitivity analyses, will be conducted during Months 3–5.
Completion of all statistical analyses is anticipated by Month 5. Manuscript drafting will occur during Months 6–7, followed by internal review and revisions. The first manuscript submission to a peer-reviewed journal is planned for Month 8.
Any additional revisions requested during peer review will be addressed promptly. Final study results and a summary of findings will be reported back to the YODA Project upon manuscript submission and again following publication, and no later than Month 12 of the data access period.
This timeline is designed to ensure completion of all analyses and dissemination of results within the approved 12-month data access window." ["project_dissemination_plan"]=> string(1345) "The primary anticipated product of this research project is a full-length manuscript reporting the results of the post hoc subgroup analyses of the THOR trial using individual participant-level data. The manuscript will focus on clinically relevant modifiers of erdafitinib efficacy, including FGFR3 alteration subtypes, prior immune checkpoint inhibitor exposure, biomarker testing characteristics, and treatment-related toxicities.
The target audience includes medical oncologists, urologists, translational cancer researchers, and clinical trialists involved in the management and development of targeted therapies for urothelial carcinoma. Findings from this study are expected to inform clinical decision-making, patient selection, and future trial design in FGFR-altered disease.
The manuscript will be submitted to a peer-reviewed oncology journal with a strong focus on genitourinary malignancies or precision oncology. Potential target journals include European Urology, Journal of Clinical Oncology, Annals of Oncology, or other comparable journals, depending on the final scope and results of the analysis.
Study results will be reported back to the YODA Project in accordance with YODA data use requirements and will be disseminated through publication and, when appropriate, presentation at scientific meetings." ["project_bibliography"]=> string(1381) "

1. Loriot Y, Matsubara N, Park SH, Huddart RA, Burgess EF, Houede N, Banek S, Guadalupi V, Ku JH, Valderrama BP, Tran B, Triantos S, Kean Y, Akapame S, Deprince K, Mukhopadhyay S, Stone NL, Siefker-Radtke AO; THOR Cohort 1 Investigators. Erdafitinib or Chemotherapy in Advanced or Metastatic Urothelial Carcinoma. N Engl J Med. 2023 Nov 23;389(21):1961-1971. doi: 10.1056/NEJMoa2308849. Epub 2023 Oct 21. PMID: 37870920.

2. Siefker-Radtke AO, Matsubara N, Park SH, Huddart RA, Burgess EF, Özgüroğlu M, Valderrama BP, Laguerre B, Basso U, Triantos S, Akapame S, Kean Y, Deprince K, Mukhopadhyay S, Loriot Y; THOR cohort 2 investigators. Erdafitinib versus pembrolizumab in pretreated patients with advanced or metastatic urothelial cancer with select FGFR alterations: cohort 2 of the randomized phase III THOR trial. Ann Oncol. 2024 Jan;35(1):107-117. doi: 10.1016/j.annonc.2023.10.003. Epub 2023 Oct 21. PMID: 37871702.

3. Matsubara N, Miura Y, Nishiyama H, Taoka R, Kojima T, Shimizu N, Hwang J, Ote T, Oyama R, Toyoizumi K, Mukhopadhyay S, Triantos S, Deprince K, Loriot Y. Phase 3 THOR Japanese subgroup analysis: erdafitinib in advanced or metastatic urothelial cancer and fibroblast growth factor receptor alterations. Int J Clin Oncol. 2024 Oct;29(10):1516-1527. doi: 10.1007/s10147-024-02583-3. Epub 2024 Jul 17. PMID: 39017806; PMCID: PMC11420312.

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2025-0924

General Information

How did you learn about the YODA Project?: Colleague

Conflict of Interest

Request Clinical Trials

Associated Trial(s):
  1. NCT03390504 - A Phase 3 Study of Erdafitinib Compared With Vinflunine or Docetaxel or Pembrolizumab in Subjects With Advanced Urothelial Cancer and Selected FGFR Gene Aberrations
What type of data are you looking for?: Individual Participant-Level Data, which includes Full CSR and all supporting documentation

Request Clinical Trials

Data Request Status

Status: Ongoing

Research Proposal

Project Title: Heterogeneity of Clinical Benefit from Erdafitinib in FGFR3-Altered Urothelial Carcinoma: A Post Hoc Subgroup Analysis of the Phase III THOR Trial

Scientific Abstract: Background
The phase III THOR trial demonstrated improved survival with erdafitinib compared with chemotherapy in patients with FGFR3-altered advanced urothelial carcinoma after immune checkpoint inhibitor (ICI) therapy. However, heterogeneity in FGFR3 alteration subtypes, prior ICI exposure, biomarker testing practices, and treatment-related toxicities has not been fully evaluated.
Objective
To identify molecular and clinical modifiers of erdafitinib efficacy using individual participant-level data from the THOR trial.
Study Design
Post hoc subgroup analyses of a randomized phase III trial.
Participants
Patients with advanced or metastatic urothelial carcinoma and confirmed FGFR3 alterations treated with erdafitinib or chemotherapy after prior ICI therapy.
Primary and Secondary Outcome Measures
Overall survival, progression-free survival and objective response rate (secondary), evaluated across FGFR3 alteration subtypes, prior ICI characteristics, FGFR testing methods, and early on-target toxicities.
Statistical Analysis
Kaplan--Meier methods and Cox proportional hazards models with interaction terms will be used. Landmark and sensitivity analyses will be performed as appropriate.

Brief Project Background and Statement of Project Significance: Background
Fibroblast growth factor receptor (FGFR) alterations define a molecularly distinct subset of urothelial carcinoma and represent an established therapeutic target. Erdafitinib, an oral pan-FGFR inhibitor, demonstrated a significant overall survival benefit over chemotherapy in the phase III THOR trial among patients with advanced urothelial carcinoma harboring FGFR3 alterations after immune checkpoint inhibitor (ICI) therapy. These results led to regulatory approval and incorporation of erdafitinib into treatment algorithms for FGFR-altered disease.
Despite this advance, FGFR3-altered urothelial carcinoma encompasses substantial biological and clinical heterogeneity. FGFR3 alterations include multiple activating point mutations and fusion variants, which may differ in oncogenic signaling, tumor biology, and therapeutic sensitivity. In addition, patients enrolled in THOR had heterogeneous prior ICI exposure, variable biomarker testing strategies (central versus local testing, tissue versus blood-based assays), and diverse treatment-related toxicity profiles. These sources of heterogeneity were not fully addressed in the primary trial analyses, leaving uncertainty regarding which patient subsets derive the greatest and most durable benefit from FGFR inhibition.
Project Significance
This project seeks to address these knowledge gaps through post hoc analyses of individual participant-level data from the THOR trial obtained via the YODA Project. By systematically evaluating molecular subtypes of FGFR3 alterations, prior ICI treatment characteristics, biomarker testing practices, and early on-target toxicities, this study aims to identify clinically meaningful modifiers of erdafitinib efficacy.
The significance of this work lies in its potential to refine patient selection and optimize treatment sequencing for FGFR-targeted therapy in urothelial carcinoma. Rather than treating FGFR3-altered disease as a binary entity, this study will provide a more nuanced framework for understanding variability in treatment benefit. Importantly, the findings are expected to be generalizable beyond the THOR trial, informing real-world clinical decision-making and the design of future clinical trials evaluating FGFR inhibitors or combination strategies.
By leveraging rigorously collected randomized trial data and applying bias-aware analytical approaches, this project will materially enhance scientific understanding of FGFR-driven urothelial carcinoma and contribute actionable insights to precision oncology and public health.

Specific Aims of the Project: Specific Aims of the Project
The overall objective of this project is to identify molecular and clinical modifiers of treatment benefit from erdafitinib in patients with advanced urothelial carcinoma harboring FGFR3 alterations, using individual participant-level data from the phase III THOR trial.
Aim 1. To evaluate whether the efficacy of erdafitinib differs according to FGFR3 alteration subtype.
Hypothesis: Patients with activating FGFR3 point mutations and those with FGFR3 fusion variants derive differential clinical benefit from erdafitinib, reflecting biological heterogeneity within FGFR3-altered disease.
Aim 2. To assess the impact of prior immune checkpoint inhibitor (ICI) exposure on outcomes with erdafitinib.
Hypothesis: Characteristics of prior ICI therapy, including treatment duration and response patterns, modify subsequent survival outcomes following FGFR inhibition.
Exploratory Aim. To examine the influence of biomarker testing practices and treatment-related toxicities on erdafitinib efficacy.
Hypothesis: Variability in FGFR testing (central vs local testing, tissue vs blood-based assays, and timing of sample acquisition) and the early development of on-target toxicities are associated with differences in clinical outcomes.
Through these aims, this study seeks to move beyond a binary classification of FGFR3-altered urothelial carcinoma and provide a more refined framework for patient selection and therapeutic decision-making with FGFR inhibitors.

Study Design: Individual trial analysis

What is the purpose of the analysis being proposed? Please select all that apply.: New research question to examine treatment effectiveness on secondary endpoints and/or within subgroup populations New research question to examine treatment safety Confirm or validate previously conducted research on treatment effectiveness

Software Used: RStudio

Data Source and Inclusion/Exclusion Criteria to be used to define the patient sample for your study: Data for this study will be obtained from the phase III THOR trial through the YODA Project. Only individual participant-level data from the THOR trial will be used. No data from external studies or other data sources will be included, and no data pooling or meta-analysis with non-YODA datasets is planned.
The study population will include all patients enrolled in the THOR trial who met the original trial eligibility criteria and were randomized to receive erdafitinib or investigator's choice chemotherapy. Key inclusion criteria applied for this analysis are: adults with advanced or metastatic urothelial carcinoma; documented FGFR3 alterations as defined by the trial protocol; prior treatment with at least one immune checkpoint inhibitor; and availability of relevant baseline, treatment, and outcome data.
No additional exclusion criteria beyond those specified in the original THOR trial protocol will be applied. Patients will not be excluded on the basis of FGFR3 alteration subtype, prior immune checkpoint inhibitor characteristics, biomarker testing method (central or local), specimen type (tissue or blood), timing of sample acquisition, or treatment-related adverse events, as these factors constitute the primary variables of interest for the proposed subgroup analyses.
All analyses will be conducted using individual participant-level data within the secure YODA analysis environment, without aggregation of summary-level data across studies.

Primary and Secondary Outcome Measure(s) and how they will be categorized/defined for your study: Primary and Secondary Outcome Measures
The primary outcome measure for this study is overall survival (OS), defined as the time from randomization in the THOR trial to death from any cause. Patients alive at the time of data cutoff will be censored at the date of last known follow-up. OS was selected as the primary endpoint to ensure consistency with the primary endpoint of the THOR trial and to allow direct comparison with previously reported results.
Secondary outcome measures include progression-free survival (PFS) and objective response rate (ORR). PFS is defined as the time from randomization to radiographic disease progression or death from any cause, whichever occurs first, according to the criteria used in the original trial protocol. Patients without documented progression or death will be censored at the date of last disease assessment. ORR is defined as the proportion of patients achieving a complete or partial response, as assessed per trial-defined response criteria.
All outcome measures will be analyzed within clinically and biologically relevant subgroups, including FGFR3 alteration subtype (activating point mutations vs fusion variants), characteristics of prior immune checkpoint inhibitor therapy, biomarker testing methods (central vs local testing, tissue vs blood-based assays, and timing of sample acquisition), and the occurrence of early on-target treatment-related adverse events.
No changes to the definitions of the primary or secondary outcome measures are planned for the final analysis or publication. Outcomes will be reported using definitions consistent with the original THOR trial to ensure transparency, reproducibility, and comparability with existing literature.

Main Predictor/Independent Variable and how it will be categorized/defined for your study: The primary independent variable is treatment assignment, defined as randomization to erdafitinib versus investigator's choice chemotherapy in the THOR trial. Treatment assignment will be used as the main exposure variable for analyses of overall survival, progression-free survival, and objective response rate.
Key independent variables for effect modification analyses include FGFR3 alteration subtype, prior immune checkpoint inhibitor (ICI) exposure, FGFR biomarker testing characteristics, and treatment-related toxicities. FGFR3 alterations will be categorized as activating point mutations versus fusion variants. Prior ICI exposure will be defined by treatment duration and response pattern, and by ICI agent when available. FGFR testing will be categorized by testing source (central vs local), specimen type (tissue vs blood-based assays), and timing of sample acquisition (archival vs recent). Treatment-related adverse events will be evaluated in exploratory analyses, focusing on early on-target toxicities characteristic of FGFR inhibition, using clinically appropriate time windows to minimize bias.
All independent variables will be defined using data available in the THOR trial dataset and applied consistently across analyses to ensure reproducibility and comparability with final published results.

Other Variables of Interest that will be used in your analysis and how they will be categorized/defined for your study: Additional variables will be used to characterize the study population and for multivariable risk adjustment in survival analyses. Demographic variables will include age at randomization (continuous) and sex (male vs female). Baseline clinical characteristics will include Eastern Cooperative Oncology Group (ECOG) performance status (0--1 vs 2), presence of visceral metastases (yes vs no), and primary tumor site.
Disease-related variables will include prior lines of systemic therapy (continuous and categorized as <=2 vs >2), prior platinum-based chemotherapy (yes vs no), and time from initial diagnosis to randomization. When available, baseline laboratory or disease burden indicators reported in the trial dataset will be incorporated as covariates.
Treatment-related variables will include treatment arm (erdafitinib vs chemotherapy), chemotherapy type in the control arm (docetaxel vs vinflunine), starting dose of erdafitinib, dose modifications (yes vs no), and treatment duration. Geographic region, as defined in the original trial, will be included to account for potential regional differences.
All covariates will be defined using trial-reported data elements and categorized in alignment with the original THOR trial protocol where applicable. These variables will be included in multivariable Cox proportional hazards models to adjust for potential confounding and to ensure robust estimation of treatment effects.

Statistical Analysis Plan: All analyses will be conducted using individual participant-level data from the THOR trial within the secure YODA analysis environment. Statistical analyses will follow a predefined analysis plan and will be performed using standard statistical software.
Descriptive Analyses
Baseline demographic, clinical, molecular, and treatment-related characteristics will be summarized by treatment arm using appropriate descriptive statistics. Continuous variables will be reported as means with standard deviations or medians with interquartile ranges, as appropriate, and categorical variables as counts and percentages. Between-group comparisons will be performed using chi-square or Fisher's exact tests for categorical variables and t-tests or non-parametric tests for continuous variables, as appropriate.
Primary and Secondary Outcome Analyses
Overall survival (OS) and progression-free survival (PFS) will be analyzed using the Kaplan--Meier method, with differences between treatment groups assessed using log-rank tests. Median survival times and survival rates at selected time points will be reported with corresponding confidence intervals. Cox proportional hazards regression models will be used to estimate hazard ratios and 95% confidence intervals.
Multivariable Cox models will be constructed to adjust for prespecified covariates, including age, sex, ECOG performance status, presence of visceral metastases, prior lines of therapy, geographic region, and treatment arm. Proportional hazards assumptions will be evaluated using standard diagnostic methods.
Objective response rate (ORR) will be compared between treatment groups using chi-square or Fisher's exact tests, and effect estimates will be reported with corresponding confidence intervals.
Subgroup and Effect Modification Analyses
Prespecified subgroup analyses will be conducted to evaluate effect modification of treatment assignment across clinically relevant variables, including FGFR3 alteration subtype, prior immune checkpoint inhibitor (ICI) exposure characteristics, and FGFR biomarker testing features. Interaction terms between treatment assignment and subgroup variables will be included in Cox models to formally assess heterogeneity of treatment effects. Subgroup analyses will be interpreted as exploratory.
Analysis of Treatment-Related Toxicities
The association between early on-target treatment-related adverse events and clinical outcomes will be explored. To minimize time-dependent bias, landmark analyses will be performed at predefined time points, and sensitivity analyses using time-dependent covariates in Cox models will be conducted when appropriate.
Sensitivity Analyses
Sensitivity analyses will be performed to assess the robustness of findings, including analyses stratified by chemotherapy type in the control arm and by biomarker testing source (central vs local). Additional analyses excluding patients with missing key covariates may be conducted as appropriate.
Missing Data
Missing data will be described for all key variables. Primary analyses will be conducted using available-case data. When appropriate, sensitivity analyses will be performed to evaluate the potential impact of missing data on study findings.
All statistical tests will be two-sided, and results will be interpreted in the context of multiple exploratory analyses without formal adjustment for multiplicity.

Narrative Summary: The phase III THOR trial showed a survival benefit of erdafitinib in FGFR3-altered advanced urothelial carcinoma after immune checkpoint inhibitor (ICI) therapy. Using YODA individual patient-level data, we will identify modifiers of erdafitinib efficacy in post hoc analyses. We will compare treatment benefit by FGFR3 alteration subtype (hotspot mutations vs fusion variants), by prior ICI exposure (agent, duration, response pattern), and by FGFR testing characteristics (central vs local; tissue vs blood; archival vs recent sampling). We will also explore whether early on-target toxicities of FGFR inhibition are associated with outcomes using bias-aware methods. Results will refine patient selection and guide sequencing of FGFR inhibition in urothelial carcinoma.

Project Timeline: The anticipated project start date is within one month of data access approval through the YODA Project, following completion of the Data Use Agreement and access setup.
During Months 1--2, data familiarization, data cleaning, and confirmation of variable definitions will be completed. Primary and secondary statistical analyses, including prespecified subgroup and sensitivity analyses, will be conducted during Months 3--5.
Completion of all statistical analyses is anticipated by Month 5. Manuscript drafting will occur during Months 6--7, followed by internal review and revisions. The first manuscript submission to a peer-reviewed journal is planned for Month 8.
Any additional revisions requested during peer review will be addressed promptly. Final study results and a summary of findings will be reported back to the YODA Project upon manuscript submission and again following publication, and no later than Month 12 of the data access period.
This timeline is designed to ensure completion of all analyses and dissemination of results within the approved 12-month data access window.

Dissemination Plan: The primary anticipated product of this research project is a full-length manuscript reporting the results of the post hoc subgroup analyses of the THOR trial using individual participant-level data. The manuscript will focus on clinically relevant modifiers of erdafitinib efficacy, including FGFR3 alteration subtypes, prior immune checkpoint inhibitor exposure, biomarker testing characteristics, and treatment-related toxicities.
The target audience includes medical oncologists, urologists, translational cancer researchers, and clinical trialists involved in the management and development of targeted therapies for urothelial carcinoma. Findings from this study are expected to inform clinical decision-making, patient selection, and future trial design in FGFR-altered disease.
The manuscript will be submitted to a peer-reviewed oncology journal with a strong focus on genitourinary malignancies or precision oncology. Potential target journals include European Urology, Journal of Clinical Oncology, Annals of Oncology, or other comparable journals, depending on the final scope and results of the analysis.
Study results will be reported back to the YODA Project in accordance with YODA data use requirements and will be disseminated through publication and, when appropriate, presentation at scientific meetings.

Bibliography:

1. Loriot Y, Matsubara N, Park SH, Huddart RA, Burgess EF, Houede N, Banek S, Guadalupi V, Ku JH, Valderrama BP, Tran B, Triantos S, Kean Y, Akapame S, Deprince K, Mukhopadhyay S, Stone NL, Siefker-Radtke AO; THOR Cohort 1 Investigators. Erdafitinib or Chemotherapy in Advanced or Metastatic Urothelial Carcinoma. N Engl J Med. 2023 Nov 23;389(21):1961-1971. doi: 10.1056/NEJMoa2308849. Epub 2023 Oct 21. PMID: 37870920.

2. Siefker-Radtke AO, Matsubara N, Park SH, Huddart RA, Burgess EF, Özgüroğlu M, Valderrama BP, Laguerre B, Basso U, Triantos S, Akapame S, Kean Y, Deprince K, Mukhopadhyay S, Loriot Y; THOR cohort 2 investigators. Erdafitinib versus pembrolizumab in pretreated patients with advanced or metastatic urothelial cancer with select FGFR alterations: cohort 2 of the randomized phase III THOR trial. Ann Oncol. 2024 Jan;35(1):107-117. doi: 10.1016/j.annonc.2023.10.003. Epub 2023 Oct 21. PMID: 37871702.

3. Matsubara N, Miura Y, Nishiyama H, Taoka R, Kojima T, Shimizu N, Hwang J, Ote T, Oyama R, Toyoizumi K, Mukhopadhyay S, Triantos S, Deprince K, Loriot Y. Phase 3 THOR Japanese subgroup analysis: erdafitinib in advanced or metastatic urothelial cancer and fibroblast growth factor receptor alterations. Int J Clin Oncol. 2024 Oct;29(10):1516-1527. doi: 10.1007/s10147-024-02583-3. Epub 2024 Jul 17. PMID: 39017806; PMCID: PMC11420312.