CD274 and neoplasm: CTCs were detected in 25/38 samples with an average of 4.5 cells/ml. After initiation of radiation therapy, the proportion of PD-L1(+) CTCs increased significantly, indicating upregulation of PD-L1 in tumour cells in response to radiation. In addition, patients positive for PD-L1 (≥5% of CTCs positive for PD-L1) at baseline had shorter PFS. Gene expression analysis showed that higher levels of PD-L1 were associated with poor prognosis.