针对生存数据删失问题,提出自适应实验框架提升因果效应估计效率。
Adaptive Experimentation for Censored Survival Outcomes
- 基于删失数据的效率边界,推导出最优分配策略。
- 相比随机分配,显著提升估计效率,减少样本需求。
- 适用于癌症等生存分析场景,适合临床试验设计者。
自适应实验可高效估计因果效应,但现有方法不适用于存在删失的生存数据(如癌症试验中的总生存期,伴随患者脱落)。本文提出一种新型自适应实验框架,用于在右删失条件下估计平均生存效应曲线。我们推导了平均生存效应曲线的半参数效率边界,并据此获得闭式表达的效率最优分配策略。该策略通过优先分配使事件与删失动态均带来高不确定性的患者亚组,推广了经典Neyman分配至生存场景。在此基础上,提出自适应生存估计器(ASE),可顺序学习分配策略并估计平均生存效应曲线。框架具备三大优势:(i) 允许使用任意机器学习模型进行扰动项估计;(ii) 基于闭式效率最优分配策略;(iii) 拥有强理论保障,包括通过鞅中心极限定理实现渐近正态性。在多种数值实验中验证,本框架相较均匀随机化和忽略删失的基线方法,持续实现效率提升。
原文摘要 · Abstract (English)
Adaptive experimentation enables efficient estimation of causal effects, but existing methods are not designed for survival data with censoring, where event times are only partially observed (e.g., overall survival in cancer trials but with dropout). In this paper, we develop a novel framework for adaptive experimentation to estimate causal effects under right censoring. For this, we derive the semiparametric efficiency bound for the average survival effect curve as a function of the treatment allocation policy and thereby obtain a closed-form efficiency-optimal allocation policy. The policy generalizes classical Neyman allocation to survival settings by prioritizing patient strata where both event and censoring dynamics induce high uncertainty. Building on this, we propose the Adaptive Survival Estimator (ASE), an adaptive framework that learns the allocation policy and estimates the average survival effect curve sequentially. Our framework has three main benefits: (i) it accommodates arbitrary machine learning models for nuisance estimation; (ii) it is guided by a closed-form efficiency-optimal allocation policy; and (iii) it admits strong theoretical guarantees, including asymptotic normality via a martingale central limit theorem. We demonstrate our framework across various numerical experiments to show consistent efficiency gains over uniform randomization and censoring-agnostic baselines.
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