Reproducibility in PD-L1 Immunohistochemistry Quantification through the Tumor Proportion Score and the Combined...

Area of Science:

• Oncology
• Pathology
• Immunohistochemistry

Background:

• Accurate quantification of Programmed Death-Ligand 1 (PD-L1) expression is crucial for guiding immunotherapy in cancer treatment.
• Standardization of PD-L1 scoring methods is essential to ensure consistent patient stratification and treatment selection.

Purpose of the Study:

• To evaluate the inter- and intra-pathologist agreement in quantifying PD-L1 expression using tumor proportion score (TPS) and combined positive score (CPS).
• To compare the reproducibility of PD-L1 quantification between single PD-L1 immunohistochemistry (S-IHC) and double immunohistochemistry (D-IHC).

Main Methods:

• Four pathologists assessed PD-L1 expression (TPS and CPS) on 60 digital IHC slides (S-IHC and D-IHC) from 15 cancer samples, twice.
• Intraclass correlation coefficients (ICC) were calculated to measure inter- and intra-pathologist agreements.

Main Results:

• Both S-IHC and D-IHC demonstrated excellent to good agreement for TPS (ICC > 0.9) and CPS (ICC > 0.75).
• D-IHC showed slightly higher agreement than S-IHC.
• S-IHC yielded higher mean TPS and CPS values compared to D-IHC.

Conclusions:

• High reproducibility in PD-L1 expression quantification is achievable with both S-IHC and D-IHC methods.
• These findings support the reliability of current IHC techniques for PD-L1 assessment in clinical practice.