Communication-Efficient Federated Risk Difference Estimation for Time-to-Event Clinical Outcomes
This study addresses the challenge of absolute survival risk estimation in multi-center medical research, where privacy constraints and reliance on a central server hinder clinically interpretable inference. Existing federated learning approaches typically yield only relative effect measures and lack interpretability for absolute risk. To overcome these limitations, we propose FedRD, a novel server-agnostic and communication-efficient federated framework for estimating risk differences. FedRD requires only one round of communication under stratified settings or three rounds in non-stratified scenarios, enabling confidence interval construction and hypothesis testing directly from distributed survival data. Theoretically, the non-stratified variant is shown to be asymptotically equivalent to centralized analysis. Extensive experiments on both simulated and real-world multinational datasets demonstrate that FedRD substantially outperforms local analyses and existing federated baselines, delivering privacy-preserving, interpretable, and statistically inferable absolute risk estimates.