PD-L1 Testing and Squamous Cell Carcinoma of the Head and Neck: A Multicenter Study on the Diagnostic Reproducibility...

Area of Science:

• Oncology
• Immunology
• Pathology

Background:

• Immune checkpoint inhibitors targeting the PD-1/PD-L1 axis are approved for advanced head and neck squamous cell carcinoma (HNSCC).
• Accurate assessment of PD-L1 expression via Combined Positive Score (CPS) is crucial for treatment selection.
• Variability in PD-L1 scoring methods may impact clinical decision-making.

Purpose of the Study:

• To compare different methods for determining PD-L1 CPS in HNSCC.
• To assess the diagnostic agreement and inter-observer reliability of these methods.
• To identify potential sources of error in PD-L1 expression evaluation.

Main Methods:

• Analysis of 40 HNSCC tissue microarrays using five distinct protocols for PD-L1 CPS assessment.
• Calculation of error rates, sensitivity, and specificity for each protocol.
• Statistical analysis of inter-observer agreement using Intraclass Correlation Coefficient (ICC).

Main Results:

• Individual protocol error rates varied from 7% to 21%, with sensitivity ranging from 79% to 96% and specificity from 50% to 100%.
• Underestimation of PD-L1 expression was common in the intermediate CPS group (1 ≤ CPS < 20).
• No single protocol accurately identified all strong PD-L1 expressors; overall inter-observer agreement was 87% with moderate reliability (ICC = 0.774).

Conclusions:

• Current methods for evaluating PD-L1 CPS in HNSCC exhibit moderate inter-observer reliability.
• Discrepancies in scoring can occur, particularly with intermediate and strong PD-L1 expression.
• Standardized training programs are necessary to enhance the consistency and accuracy of PD-L1 CPS assessment in HNSCC for optimal patient care.