Multiplex immunohistochemistry/immunofluorescence (mIHC/IF) for PD-L1 testing in triple-negative breast cancer: a...

Area of Science:

• Oncology
• Immunology
• Pathology

Background:

• Programmed death-ligand 1 (PD-L1) antibody therapy is approved for metastatic triple-negative breast cancer (TNBC), particularly in PD-L1 positive subgroups.
• The SP142 PD-L1 clone, used in the IMpassion130 trial, showed variability in previous lung cancer harmonization studies.
• Assessing PD-L1 clone comparability is crucial for accurate patient stratification in TNBC immunotherapy.

Purpose of the Study:

• To evaluate the concordance between conventional immunohistochemistry (IHC) and multiplex immunohistochemistry/immunofluorescence (mIHC/IF) for PD-L1 assessment in TNBC.
• To compare three different PD-L1 antibody clones (22C3, SP142, SP263) simultaneously using mIHC/IF.

Main Methods:

• A cohort of 25 TNBC cases, 12 non-small-cell lung carcinomas, and 8 other cancers were analyzed.
• Conventional IHC and mIHC/IF techniques were employed to detect PD-L1 expression.
• Epithelial cell adhesion molecule (EpCAM) labeling distinguished tumor cells from immune cells.

Main Results:

• Moderate-to-strong correlations were observed between mIHC/IF and conventional IHC for PD-L1 positivity.
• Individual concordance rates across different PD-L1 clones ranged from 67% to 100%.
• Spearman's rank correlation coefficients reached up to 0.88, indicating good agreement.

Conclusions:

• mIHC/IF is a promising tool for simultaneously detecting and quantifying multiple PD-L1 clones in cancer immunotherapy.
• This method enables accurate evaluation of both tumor and immune cells, crucial for predicting patient response to anti-PD-1/PD-L1 therapy.
• Further harmonization and analysis are essential for integrating mIHC/IF into routine diagnostic settings for challenging cancers.