PD-L1 expression in head and neck cancer tissue specimens decreases with time

Background: PD-L1 immunohistochemical expression is used as an important theranostic marker in various malignancies, including head and neck squamous cell carcinoma (HNSCC) where the combined positive score (CPS) guides treatment decisions. Despite indirect evidence that there is loss of antigenicity for archived tissues, there is no direct comparison between PD-L1 expression of the same tissue upon arrival and after its storage.Material and Methods: We compared the immunohistochemical expression of PD-L1 (22C3) in 106 HNSCC upon their arrival and after their storage (interval ranging from 20 to 48 months, mean 30.8 months). The evaluation was performed by two different pathologists' groups.Results: We found a statistically significant decrease in the PD-L1 tumor proportional score (TPS), immune cells expression (IC) and CPS between the initial and the newly stained slides.Conclusion: This is the first study comparing PD-L1 expression between a tissue and himself later in time, highlighting an important decrease in expression by tumor and immune cells, and suggesting that an immediate rather than a retrospective assay of PD-L1 expression should be preferable in the routine practice.Data Availability: Data are available upon reasonable request.

Automated summary

The study compared the PD-L1 expression in HNSCC tissues upon arrival and after storage, revealing a significant decrease in tumor proportional score and immune cells expression. Immediate assay of PD-L1 expression is preferable in routine practice to avoid decreased expression levels.