Effect of radiotherapy exposure on fruquintinib plus sintilimab treatment in refractory microsatellite stable metastatic colorectal cancer: a prospective observation study

Immune checkpoint inhibitors (ICIs) in combination with antiangiogenic drugs have shown promising outcomes in the third-line and subsequent treatments of patients with microsatellite stable metastatic colorectal cancer (MSS-mCRC). Radiotherapy (RT) may enhance the antitumor effect of immunotherapy. However, the effect of RT exposure on patients receiving ICIs and targeted therapy remains unclear. This study aimed to investigate the association between RT exposure and clinical responses to fruquintinib (a highly selective tyrosine kinase inhibitor of vascular endothelial growth factor receptor) plus sintilimab (an anti-programmed death 1 antibody; F&S) in previously treated patients with MSS-mCRC and to explore predictive biomarkers.