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.