Model-Aided Quantification of Patient-Specific Benefit in Mitigating Radiation-Induced Lymphopenia by Particle...

Treatment-related lymphopenia is a frequent and clinically significant consequence of cancer therapy that can compromise immune-mediated tumor control and worsen patient outcomes. Despite its importance, no mechanistic framework exists to accurately predict the severity of lymphopenia from patient-specific data.

Here, we present a biokinetic model that quantitatively describes lymphocyte depletion and recovery during and after radiation therapy, integrating radiation dose-volume distributions, blood circulation dynamics, and distinct kinetics of fast- and slow-recovering lymphocyte populations. The model was calibrated and validated using 56 independent clinical data sets encompassing various tumor sites and treatment modalities.

The model reproduces observed lymphocyte counts and enables prediction of individual severity of lymphopenia from baseline or early-treatment counts. Applying this framework to published clinical data, we estimate that particle therapy is associated with an ∼30% lower radiation-induced lymphocyte depletion rate than photon therapy, providing a mechanistic quantitative explanation for its observed immune-sparing effect.

By linking radiation physics, immune kinetics, and clinical outcomes, our model establishes a mechanistically grounded predictive approach for anticipating systemic immune toxicity. Beyond radiation therapy, this framework offers a generalizable strategy for integrating early biological markers into treatment optimization, advancing personalized and immune-preserving cancer therapy.