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✅   Improved Tumor Blood Flow Enhances the Abscopal Effect: Preclinical Assessment in Mice Treated with Combined Radiation and PD-1 Blockade Therapy

science

The abscopal effect, where localized radiation therapy induces regression of distant metastatic lesions through immune activation, shows promise for treating metastatic cancer but occurs inconsistently. Here we demonstrate that tumor perfusion critically influences systemic immune responses to combination therapy with radiation and PD-1 blockade. Using multimodal imaging including DCE-MRI, EPR oximetry, and hyperpolarized 13C-MRI, we show that successful abscopal responses in MC38 tumors are characterized by enhanced perfusion, reduced hypoxia, decreased cellularity, and lower glycolytic activity in remote tumors. Notably, pre-treatment perfusion metrics (AUC1min) and extracellular volume (AUC10min) in primary tumors predict subsequent growth of remote tumors, while the same measurements in remote tumors lack predictive value.

BioRxiv     May 09, 2025