CD274 and cancer: However, no such association was noted when the detection interval was longer than 6 months (r =0.19, P =0.31; Figure 6C); these findings may reflect the fact that long-term antitumor therapy had significantly changed the PD-L1 status of cancer cells, suggesting that CTC-based PD-L1 testing may be a choice when immunotherapy was considered while the latest pathological results were longer than 6 months ago.