Cost-effectiveness analyses (CEAs) compare the costs and health outcomes of treatment regimes to inform medical decisions. With observational claims data, CEAs must address nonrandom treatment assignment, administrative censoring, and irregularly spaced medical visits that reflect the continuous timing of care and treatment initiation. In high-risk, early-stage endometrial cancer (HR-EC), adjuvant radiation is initiated at patient-specific times following hysterectomy, causing confounding between treatment and outcomes that can evolve with post-surgical recovery and clinical course. Most existing CEA methods use point-treatment or discrete-time models. However, point-treatment approaches break down with time-varying confounding, while discrete-time models bin continuous time, expand the data into a person-period format, and can induce zero-inflation by creating many intervals with no cost-accruing events. We propose a Bayesian framework for CEAs with sequential decision-making that jointly models costs and event times in continuous time, accounts for administrative censoring, and supports dynamic treatment regimes with minimal parametric assumptions. We use Bayesian g-computation to estimate causally interpretable cost-effectiveness measures, including net monetary benefit, and to compare regimes through posterior contrasts. We evaluate the finite-sample performance of the proposed method in simulations across censoring levels and compare it against discrete-time and fully parametric alternatives. We then use SEER-Medicare data to assess the cost-effectiveness of initiating adjuvant radiation therapy within six months following hysterectomy among HR-EC patients.

翻译：成本效益分析通过比较不同治疗方案的成本与健康结果，为医疗决策提供依据。基于观察性索赔数据开展成本效益分析时，必须处理非随机治疗分配、行政删失以及反映持续医疗过程和治疗启动时点的不规则就诊间隔。在高风险早期子宫内膜癌治疗中，辅助放疗在子宫切除术后根据患者个体情况择时启动，导致治疗与结果间的混杂效应可能随术后恢复和临床病程动态演变。现有成本效益分析方法多采用时点治疗或离散时间模型，但时点治疗方法难以处理时变混杂，而离散时间模型将连续时间离散化，将数据扩展为人-时段格式，且可能因创建大量无成本发生事件的区间导致零膨胀问题。本文提出一种适用于连续时间序列决策的成本效益分析贝叶斯框架，该框架联合建模连续时间下的成本与事件发生时间，处理行政删失问题，并以最小参数假设支持动态治疗方案。我们采用贝叶斯g-计算法估计具有因果解释性的成本效益指标（包括净货币收益），并通过后验对比比较不同方案。通过模拟实验在不同删失水平下评估所提方法的有限样本性能，并与离散时间模型及完全参数化方法进行对比。最后利用SEER-Medicare数据评估高风险早期子宫内膜癌患者在子宫切除术后六个月内启动辅助放疗的成本效益。