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Bayesian nonparametric estimation of targeted agent effects on biomarker change to predict clinical outcome
Rebecca Graziani1, Michele Guindani2, Peter F Thall2
1Università Commerciale Luigi Bocconi, Milan, Italy.
Abstract:
The effect of a targeted agent on a cancer patient's clinical outcome putatively is mediated through the agent's effect on one or more early biological events. This is motivated by pre-clinical experiments with cells or animals that identify such events, represented by binary or quantitative biomarkers. When evaluating targeted agents in humans, central questions are whether the distribution of a targeted biomarker changes following treatment, the nature and magnitude of this change, and whether it is associated with clinical outcome. Major difficulties in estimating these effects are that a biomarker's distribution may be complex, vary substantially between patients, and have complicated relationships with clinical outcomes. We present a probabilistically coherent framework for modeling and estimation in this setting, including a hierarchical Bayesian nonparametric mixture model for biomarkers that we use to define a functional profile of pre-versus-post-treatment biomarker distribution change. The functional is similar to the receiver operating characteristic used in diagnostic testing. The hierarchical model yields clusters of individual patient biomarker profile functionals, and we use the profile as a covariate in a regression model for clinical outcome. The methodology is illustrated by analysis of a dataset from a clinical trial in prostate cancer using imatinib to target platelet-derived growth factor, with the clinical aim to improve progression-free survival time.
Insights
This study introduces a new statistical framework to analyze how targeted cancer therapies affect biomarkers and patient outcomes. It helps understand biomarker changes and their link to clinical results, improving treatment evaluation.
Area of Science:
- Biostatistics
- Translational Oncology
- Biomarker Discovery
Background:
- Targeted therapies aim to alter specific biological events in cancer patients, often measured by biomarkers.
- Evaluating these therapies requires understanding biomarker distribution changes and their association with clinical outcomes.
- Complex biomarker distributions and patient variability pose significant estimation challenges.
Purpose of the Study:
- To develop a probabilistically coherent framework for modeling biomarker changes post-treatment.
- To assess the relationship between biomarker profile shifts and clinical outcomes in cancer patients.
- To provide a robust method for evaluating targeted agent efficacy.
Main Methods:
- A hierarchical Bayesian nonparametric mixture model was developed for biomarker analysis.
- A functional profile, analogous to the receiver operating characteristic curve, was defined for pre- and post-treatment biomarker distributions.
- Patient biomarker profiles were clustered and used as covariates in clinical outcome regression models.
Main Results:
- The framework successfully models complex biomarker distributions and their changes.
- Individual patient biomarker profile functionals were clustered, revealing patient heterogeneity.
- The biomarker profile was shown to be a useful covariate in predicting clinical outcomes.
Conclusions:
- The proposed Bayesian nonparametric framework offers a coherent approach to analyzing targeted therapy effects on biomarkers and clinical outcomes.
- This methodology enhances the understanding of biomarker dynamics and their impact on treatment efficacy.
- The framework was validated using data from a prostate cancer trial targeting platelet-derived growth factor.
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