Comparable immunoreactivity rates of PD‐L1 in archival and recent specimens from non‐small cell lung cancer

BACKGROUND: Molecular targeted therapy including the use of monoclonal antibodies directed against the immune checkpoints PD‐L1 and PD‐1 receptor have remarkably improved the therapeutic response and survival of cancer patients. The tumor expression level of PD‐L1 can predict the response rate to checkpoint inhibitors. We evaluated whether the time interval between tumor tissue sampling/paraffinization and immunohistochemistry affects the staining level of PD‐L1 in non‐small cell lung cancer (NSCLC). METHODS: This study comprised 137 patients with NSCLC. Tumors were stained with 22C3 or 28‐8 antibodies. RESULTS: There was a significant correlation between the immunoreactivity rate of tumor tissues obtained using 22C3 and 28‐8 clones. No statistical difference in immunoreactivity between archival and recent samples stained either with 22C3 or 28‐8 antibodies was observed. The immunoreactivity rate achieved with 22C3 or 28‐8 antibodies significantly correlated with tumor histological type and size, but not with specimen storage time, age, gender, smoking history, clinical stage, or lymph node metastasis. CONCLUSION: In brief, the results of this study show that the time interval between tissue sampling/paraffinization and immunohistochemical analysis has no influence on the immunoreactivity rate of PD‐L1 in NSCLC.