Table 4 Head-to-Head Test Performance: Test-Validation Metrics

Anderson et al. (2016) [7]

Drug against which the study validated the test: N/A

28–8 (Dako) and SP263 (Roche)

Overall concordance between antibodies was 90.3%, but was only 66.7% for specimens considered positive for PD-L1 expression

There was considerable variation in the percentage of TC staining positive as determined by the two methods, which along with the different test cutoffs contributed to discordant results

This study points to the importance of methodological and interpretation variation, as well as other considerations such as tumor heterogeneity and dynamics of expression, when evaluating the use of PD-L1 as a biomarker of potential therapeutic response to checkpoint blockade inhibitors

McLaughlin et al. (2016) [20]

Drug against which the study validated the test: N/A

E1L3N (CST^a) and SP142 (Roche)

PD-L1 Comparison Using Different PD-L1 Antibodies and IHC

κ concordance between antibodies was low, irrespective of the cutoff used:

• 1% tumor PD-L1 cutoff: 0.340

• 5% tumor PD-L1 cutoff: 0.286

• 5% stroma PD-L1 cutoff: 0.124

• 50% tumor PD-L1 cutoff: 0.189

Concordance between the two rigorously validated antibodies was fair to poor.While both E1L3N and SP142 reportedly bind to the intracellular domain of PD-L1, the difference between the two antibodies raises concerns and suggests antibody-validation data should be shown in future clinical trial reports

Rivalland et al. (2016) [11]

Drug against which the study validated the test: N/A

E1L3N (CST^a) and 28–8 (Dako)

The concordance between antibodies was 75.0% and 86.2% at 5% and 50% cutoffs, respectively

• E1L3N stained a significantly higher proportion of tumors at both cutoffs (P < 0.001), and in almost all clinic-pathologic subgroups

• A significant correlation was observed in staining between antibodies (R² = 0.40, P < 0.0001)

• Small-cell lung cancer stained significantly more frequently than adenocarcinoma with Dako 288 (35.7% vs. 17.4%, P < 0.001) but not with E1L3N (44% vs. 35.1%, P < 0.08)

Overall PD-L1 positivity was correlated between these two antibodies, however the CST^a antibody stained significantly more samples

Scheel et al. (2016) [6]

Drug against which the study validated the test: N/A

28–8, 22C3, SP142, and SP263 (NR)

• NR

• The tests 28–8 and 22C3 stained comparable TC proportions

• In some cases, SP142 stained fewer TCs but more ICs and SP263 stained more TCs and ICs compared with the other tests

• The differences in TC proportions would translate into different classifications by any of the dichotomous cutoffs

• The data indicate that unified PD-L1 IHC scoring criteria for TCs are feasible, while scoring of ICs requires detailed training

• The four tested PD-L1 tests did not show comparable staining patterns in all cases of NSCLC

• The results obtained by each test are not interchangeable. Thus, more studies are required to archive a harmonized “PD-L1 status” in NSCLC

• In particular, more data on the predictive value of one test for multiple substances are needed

Smith et al. (2016) [15]

Drug against which the study validated the test: N/A

SP263 (Roche) and E1L3N (CST^a)

NR

Inter-pathologist correlation

Membrane tumor staining scores

• SP263: R² > 0.87

• E1L3N: R² > 0.82

Positively staining cells in the immune infiltrate

• SP263: R² > 0.66

• E1L3N: R² > 0.80

Due to its staining intensity, scoring range, and pathologist preference, the SP263 IHC test has been deemed superior to the E1L3N IHC test

Ilie et al. (2016a) [13]

Drug against which the study validated the test: N/A

SP142 and SP263 (Roche); and

28–8 (Antibodycam)

Inter-reader precision in determining the PD-L1 expression in TCs:

• OA: 92% (κ = 0.910), 98% (κ = 0.976) and 96% (κ = 0.935) for SP142, SP263 and 28–8 tests

Inter-reader precision in determining the PD-L1 expression in ICs:

• OA: 81% (κ = 0.786), 87% (κ = 0.832), and 86% (κ = 0.817) for SP142, SP263 and 28–8 tests, respectively

Concordance analysis on TCs:

• Poor correlation between the SP142 and SP263 antibodies (ρ = 0.852, κ = 0.362), and the SP142 and 28–8 antibodies (ρ = 0.860, κ = 0.412), while a good correlation was observed between the SP263 and 28–8 antibodies (ρ = 0.996, κ = 0.883)

Concordance analysis on ICs:

• Poor agreement between the SP142 and SP263 antibodies (ρ = 0.568, κ = 0.018) and the SP142 and 28–8 antibodies (ρ = 0.590, κ = 0.134), while a good correlation was noted between the SP263 and 28–8 antibodies (ρ = 0.880, κ = 0.721)

Our results suggest that PD-L1 protein expression is heterogeneous and that different antibody tests may yield variable results. The anti-PD-L1 antibodies SP142 vs. SP263, and SP142 vs. 28–8 showed fair to poor concordance, while the 28–8 and SP263 antibodies demonstrated a strong correlation for both the TC and IC compartments

Schildhaus et al. (2016) [12]

Drug against which the study validated the test: N/A

IHC: 28–8 (Dako) and FISH: ZytoLight SPEC CD274, PDCDILG2/CEN 9 Dual Color Probe

The correlation between IHC and FISH was statistically significant (χ²: P < 0.001)

NR

PD-L1/2 FISH could contribute to our understanding of PD-L1 expression and could therefore be a valuable adjunct biomarker in upcoming trials with PD-1/PD-L1 inhibitors