Research map / Probabilistic and scientific modeling / Treatment effects
Heterogeneous Treatment Effect in Time-to-Event Outcomes: Harnessing Censored Data with Recursively Imputed Trees
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Proposes MISTR, a non-parametric HTE estimator for right-censored survival data that replaces censoring-model estimation with recursively imputed survival trees (RIST) and multiple imputation over causal forests, extended to instrumental variables as MISTR-IV.
Problem
Estimating heterogeneous treatment effects on time-to-event outcomes under heavy right-censoring and possible unobserved confounding, where existing IPCW-based and causal survival forest methods degrade or cannot use instrumental variables.
Approach
Impute censored event times multiple times using recursively imputed survival trees (no explicit censoring model), fit a causal forest on each completed dataset, and pool estimates with Rubin's rule; the IV variant swaps in an instrumental forest.
Key results
- Under heavy censoring in MIMIC 1 (89.5%), MISTR achieves MSE 6.262 vs CSF 8.741 (x100).
- In IV simulation setting 204 (88% censoring), MISTR-IV achieves MAE 11.40 vs IPCW-IV 32.10 (x100).
- On ACTG 175 with added censoring, MISTR reduces MSE vs CSF (HIV-2: 1.209 vs 1.875).
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| Use MISTR instead of CSF | HTE estimation on MIMIC semi-simulated data · MIMIC 1–4 | MSE: 8.741 -> 6.262; 6.532 -> 5.891; 5.632 -> 5.200; 5.349 -> 5.034 | Helped |
| Use MISTR instead of CSF | HTE estimation on MIMIC semi-simulated data · MIMIC 5 | MSE: 5.474 -> 5.494 | No clear effect |
| Use MISTR-IV instead of IPCW-IV | HTE estimation with unobserved confounding · IV settings 200, 200-a, 200-b, 201–204-b | MAE: 26.28 -> 14.33; 31.50 -> 16.32; 42.46 -> 21.12; 35.84 -> 18.24; 33.27 -> 17.50; 27.70 -> 12.82; 32.10 -> 11.40; 36.19 -> | Helped |
| Use MISTR instead of CSF under additional censoring | HTE estimation on ACTG 175 · HIV-1, HIV-2, HIV-3 additional censoring | MSE: 1.388 -> 1.207; 1.875 -> 1.209; 1.320 -> 0.777 | Helped |
| Increase censoring rate | MISTR versus CSF on MIMIC semi-simulated data · MIMIC 1–5 | MSE | Mixed |
| Increase the number of imputations | MISTR · MIMIC 1–5 | MSE | Helped |
Surprising findings
- On the low-censoring MIMIC 5 setting (69.9%), CSF slightly outperforms MISTR in MSE (5.474 vs 5.494).
Limitations
- Relies on RIST imputation hyperparameters and requires many imputations (A>=100) and bag-size tuning for variance.
- IV estimate represents HTE among compliers and requires IV assumptions that cannot be verified; no ground truth in real data.
- Performance advantage over CSF is marginal or absent at low censoring rates.
Experimental setup
Datasets: ACTG 175 MIMIC-IV 2.0 Illinois Unemployment Insurance Experiments synthetic simulation settings 1-10 and 200-204
Benchmarks: simulation settings 1-10 MIMIC semi-simulated settings IV simulation settings 200-204 ACTG 175 with additional censoring Illinois Unemployment Insurance
Metrics: MSE MAE SEM estimated SE
Baselines: Causal Survival Forest (CSF) IPCW IPCW-IV T-learner X-learner S-learner
Builds on: causal survival forest recursively imputed survival trees causal forest instrumental forest Rubin's rule
Closest papers by meaning
- Orthogonal Survival Learners for Estimating Heterogeneous Treatment Effects from Time-to-Event Data (NeurIPS 2025 · similarity 0.89)
- Assessing the robustness of heterogeneous treatment effects in survival analysis under informative censoring (NeurIPS 2026 · similarity 0.88)
- Doubly robust identification of treatment effects from multiple environments (ICLR 2025 · similarity 0.87)
- A Non-parametric Direct Learning Approach to Heterogeneous Treatment Effect Estimation under Unmeasured Confounding (NeurIPS 2024 · similarity 0.87)
- Doubly Protected Estimation for Survival Outcomes Utilizing External Controls for Randomized Clinical Trials (ICML 2025 · similarity 0.86)
- Estimating Heterogeneous Treatment Effects by Combining Weak Instruments and Observational Data (NeurIPS 2024 · similarity 0.86)
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