CD274 and neoplasm: However, if the ratio between the tumor uptake and blood pool at 2 h was significantly correlated to the PD-L1 immunohistochemistry (ρ = 0.68, p = 0.014) and the uptake ratio was lower in tumors with ≤1% PD-L1 expression (1.89 versus 2.49, p = 0.048), the results seem too limited to be used in clinical practice [45].