ICAM-1 orchestrates the abscopal effect of tumor radiotherapy

Significance Although RT serves as a frontline therapy for more than 50% of patients with malignancies, its efficacy is limited to localized tumors. Efforts in harnessing the abscopal effect of RT could systemically eliminate metastatic lesions disseminated beyond the radiation field; however, success has been limited thus far, owing to an inadequate understanding of the underlying mechanisms and an absence of reliable biomarkers for early prediction. Here we demonstrate that noninvasive PET imaging of ICAM-1 expression confers predictive value for abscopal effect efficacy at an early stage. This strategy may also facilitate potential high-throughput screening of current or novel drugs to be used in combination with RT to achieve desired antitumor therapeutic outcomes that eliminate both primary and metastatic lesions.