Abstract

Recent exploration of the optimal individual treatment rule (ITR) for patients has attracted a lot of attentions due to the potential heterogeneous response of patients to different treatments. An optimal ITR is a decision function based on patients’ characteristics for the treatment that maximizes the expected clinical outcome. Current literature mainly focuses on two types of methods, model-based and classification-based methods. Model-based methods rely on the estimation of conditional mean of outcome instead of directly targeting decision boundaries for the optimal ITR. As a result, they may yield suboptimal decisions. In contrast, although classification based methods directly target the optimal ITR by converting the problem into weighted classification, these methods rely on using correct weights for all subjects, which may cause model misspecification. To overcome the potential drawbacks of these methods, we propose a simple and flexible one-step method to directly learn (D-learning) the optimal ITR without model and weight specifications. Multi-category D-learning is also proposed for the case with multiple treatments. A new effect measure is proposed to quantify the relative strength of an treatment for a patient. We show estimation consistency and establish tight finite sample error bounds for the proposed D-learning. Numerical studies including simulated and real data examples are used to demonstrate the competitive performance of D-learning.

Highlights

  • Precision Medicine has recently gained increasing attention in scientific research

  • We propose a novel one-step method to directly learn (Dlearning) the optimal individual treatment rule (ITR) without specifying the main effect model and weights for both binary and multiple treatment settings, and simultaneously perform variable selection on prescriptive variables for linear models

  • We propose a direct learning (D-learning) method to estimate the optimal ITR by reformulating the optimal decision function

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Summary

Introduction

Precision Medicine has recently gained increasing attention in scientific research. The goal of precision medicine is to identify the optimal individual treatment rule (ITR) by considering the patients’ heterogeneity, such as demographics, background and genetic information, to maximize each patient’s expected clin-. Modern variable selection techniques have been used in model-based methods, they mainly focus on variables for prediction and may neglect the prescriptive variables that have weak predictive power but are important for decision making This may cause the mismatch between predicting clinical outcomes and optimizing ITRs for model-based methods. [27] proposed a sparse OWL under the classification framework for variable selection Despite these existing methods, more developments are needed for effective ITR estimation. We propose a novel one-step method to directly learn (Dlearning) the optimal ITR without specifying the main effect model and weights for both binary and multiple treatment settings, and simultaneously perform variable selection on prescriptive variables for linear models.

Direct learning for individual treatment rules
D-learning
D-learning for linear decision rules
D-learning for nonlinear decision rules
Multi-category D-learning
Tuning parameter selection
Theoretical properties of D-learning
Consistency and value reduction bounds under linear decision rules
Value reduction bounds under nonlinear decision rules
Simulation study
Linear decision boundary study
Nonlinear decision boundary study
Multi-category linear decision boundary study
Applications to AIDS clinical data
Pairwise comparison
Overall comparison
Discussion
Findings
More simulation results
Full Text
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