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. Author manuscript; available in PMC: 2019 Jan 1.
Published in final edited form as: Cancer J. 2018 Jan-Feb;24(1):41–46. doi: 10.1097/PPO.0000000000000301

Table 2.

Patients whose tumors are PD-L1+ and who do not respond to anti-PD-(L)1 as well as patients whose tumors are PD-L1- and who do respond may be attributable to numerous factors potentially limiting the sensitivity and specify of the available IHC assays.

PD-L1(+) non-responders PD-L1(−) responders
Assay performance and threshold for positivity Assay performance and threshold for positivity
Exclusive constitutive PD-L1 expression Exclusive immune cell PD-L1 expression
Spatial and temporal expression heterogeneity Spatial and temporal expression heterogeneity
Limited sampling Limited sampling
Alternate PD-1/PD-L1 ligand/receptor activity Alternate PD-1/PD-L1 ligand/receptor activity
Other inhibitory checkpoints/mechanisms