Optimal Individualized Treatment Rule for Combination Treatments Under Budget Constraints

TL;DR

This paper introduces a novel nonparametric Double Encoder Model for estimating optimal combination treatment rules tailored to individual characteristics, effectively incorporating complex effects and respecting budget constraints, with proven superior performance.

Contribution

The paper proposes a new Double Encoder Model for combination treatments that improves estimation efficiency and incorporates budget constraints via a multi-choice knapsack formulation.

Findings

Outperforms existing ITR estimation methods in simulations.

Demonstrates effectiveness in colorectal cancer treatment data.

Provides theoretical bounds and convergence rates for the proposed method.

Abstract

The individualized treatment rule (ITR), which recommends an optimal treatment based on individual characteristics, has drawn considerable interest from many areas such as precision medicine, personalized education, and personalized marketing. Existing ITR estimation methods mainly adopt one of two or more treatments. However, a combination of multiple treatments could be more powerful in various areas. In this paper, we propose a novel Double Encoder Model (DEM) to estimate the individualized treatment rule for combination treatments. The proposed double encoder model is a nonparametric model which not only flexibly incorporates complex treatment effects and interaction effects among treatments, but also improves estimation efficiency via the parameter-sharing feature. In addition, we tailor the estimated ITR to budget constraints through a multi-choice knapsack formulation, which enhances our proposed method under restricted-resource scenarios. In theory, we provide the value reduction bound with or without budget constraints, and an improved convergence rate with respect to the number of treatments under the DEM. Our simulation studies show that the proposed method outperforms the existing ITR estimation in various settings. We also demonstrate the superior performance of the proposed method in PDX data that recommends optimal combination treatments to shrink the tumor size of the colorectal cancer.