Reliability of PD-L1 assays using small tissue samples compared with surgical specimens

Area of Science:

• Oncology
• Immunology
• Diagnostic Pathology

Background:

• Programmed death ligand 1 (PD-L1) immunohistochemistry (IHC) assays are crucial for guiding immune checkpoint inhibitor therapy in non-small cell lung cancer (NSCLC).
• Limited data exists on the clinical reliability of PD-L1 IHC assays when performed on small biopsy samples, which are often used for initial diagnosis.

Purpose of the Study:

• To evaluate the clinical reliability of three commercial PD-L1 IHC assays (22C3, SP142, SP263) using small biopsy samples from NSCLC patients.
• To compare PD-L1 expression levels determined from small biopsies against those from surgical specimens, considered the reference standard.

Main Methods:

• A cohort of 46 NSCLC patients underwent PD-L1 testing on both small biopsy samples and surgical specimens using three distinct PD-L1 IHC assays.
• PD-L1 expression was analyzed using cut-off values of 1%, 5%, 10%, and 50%, with concordance rates calculated against surgical specimen results.
• Various biopsy techniques were employed, including radial probe endobronchial ultrasound, transbronchial needle aspiration, bronchoscopic biopsy, and percutaneous needle aspiration.

Main Results:

• Concordance rates for the 22C3, SP142, and SP263 assays ranged from 73-96%, 65-80%, and 72%-91%, respectively, when compared to surgical specimens.
• The study demonstrated that PD-L1 IHC testing on small biopsy samples is generally reliable across the evaluated commercial assays.

Conclusions:

• Commercial PD-L1 IHC assays demonstrate reliable performance when utilizing small biopsy samples in non-small cell lung cancer patients.
• These findings support the use of small biopsy samples for PD-L1 testing, facilitating timely treatment decisions for NSCLC patients receiving immune checkpoint inhibitors.