Comparison of Two Antibodies for The Detection of PD-L1 Expression in Non-Small Cell Lung Cancer

Objective This study aims to evaluate the PD-L1 expression testing concordance in Chinese non-small cell lung cancer （NSCLC） using two antibodies of SP142 and E1L3N. Methods Tissue samples of a consecutive 158 cases of NSCLC were made into formalin-fixed and paraffin embedded （FFPE） blocks. Optimized immunohistochemistry （IHC） using SP142 and E1L3N were established and then PD-L1 expression tests were carried out on the cancer tissue samples and immune cells. Tumor proportion score （TPS） and Histo-Score （HScore） were calculated for the evaluation of PD-L1 expression. Chi square test and bivariate correlation test were performed for the statistical analysis of the data. Results In the cohort of 158 cases of NSCLC, PD-L1 expression positivity by SP142 and E1L3N were 54.4% （86/158） and 62.7% （99/158） separately. The staining patterns of these two antibodies on tumor cells were similar. When TPS set in intervals of 1%≤TPS<5%, 5%≤TPS<50%, TPS≥50%, PD-L1 positivity by SP142 were 6.3%, 17.1% and 24.1%, and positivity by E1L3N were 7.6%, 22.8% and 26.6% separately, showing the similar results by two antibodies （P=0.368）. Taking staining intensity into account, bivariate test showed HScore values of two antibodies had good correlation （r=0.624, P=0.001）. However, in all positive samples if cut-point set as TPS≥5% or TPS≥50%, there are discrepancies of 43.9% （40/91） or 42.0% （21/50） of PD-L1 positivity between the two antibodies. In evaluating immune cells, the staining patterns of the two antibodies were heterogeneous, and if cut-off set at 1%, positivity of PD-L1 expression in immune cells were 19.6% and 16.5% separately. Conclusion Antibodies of SP142 and E1L3N have good concordance in terms of PD-L1 detection rate and staining patterns under the condition of optimized IHC. IHC by the two antibodies may be complimentary to detect PD-L1 positive cases as more as possible for clinical reference.