Comparing Three Different Anti–Programmed Death-Ligand 1 Antibodies in Immunohistochemical Evaluation of Combined Chemoimmunotherapy Response in Patients With NSCLC: A Prospective Study

Introduction

Multiple programmed death-ligand 1 (PD-L1) immunohistochemistry assays performed using different antibodies including DAKO 22C3, DAKO 28-8, and Ventana SP142 PD-L1—predictive markers for response to various immune checkpoint inhibitors in NSCLC—have been approved in several countries. The differences in multiple PD-L1 immunohistochemistry assay results in predicting the therapeutic response to combined chemoimmunotherapy in patients with NSCLC remain unclear.

Methods

In this multicenter prospective observational study, we monitored 70 patients with advanced NSCLC treated with combined chemoimmunotherapy at 10 institutions in Japan. The expression of PD-L1 in pretreatment tumors was evaluated using the 22C3, 28-8, and SP142 assays in all patients.

Results

The PD-L1 level in tumor cells determined using the 22C3 assay was the highest among the three assays performed with different antibodies. According to the 22C3 assay results, the PD-L1 tumor proportion score greater than or equal to 50% group had a significantly longer progression-free survival period than the PD-L1 tumor proportion score less than 50% group. Nevertheless, the other assays did not reveal remarkable differences in the objective response rate or progression-free survival.

Conclusions

In our study, PD-L1 expression determined using the 22C3 assay was more correlated with the therapeutic response of patients with NSCLC treated with combined chemoimmunotherapy than that determined using the 28-8 and SP142 assays. Therefore, the 22C3 assay may be useful for clinical decision-making for patients with NSCLC treated with combined chemoimmunotherapy. Trial registration number: UMIN 000043958.