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Programmed Death-Ligand 1 Expression in Triple-Negative Breast Cancer: Insights from a Mexican Cohort
Cynthia Villarreal-Garza1, César Octavio Lara-Torres2, Jesus Edgardo Hernandez-Hernandez3
1Oncology Institute and Breast Cancer Center, Hospital Zambrano Hellion TecSalud, Tecnologico de Monterrey, San Pedro Garza Garcia 66260, Mexico.
Cancers
|July 28, 2026
Summary
In Mexican women with triple-negative breast cancer (TNBC), PD-L1 positivity was found in 29.1% of patients. This PD-L1 expression varied significantly between biopsy and surgical specimens, impacting treatment decisions.
Area of Science:
- Oncology
- Immunology
- Genetics
Background:
- Pembrolizumab is standard for triple-negative breast cancer (TNBC), but metastatic treatment relies on PD-L1 expression.
- PD-L1 prevalence varies by ethnicity, necessitating local data for treatment optimization.
- Mexican TNBC patient data on PD-L1 expression was lacking.
Purpose of the Study:
- To characterize PD-L1 positivity rates in a Mexican TNBC cohort.
- To define the local molecular landscape of PD-L1 expression in Mexican TNBC patients.
- To explore associations between PD-L1 expression and clinicopathological features.
Main Methods:
- Retrospective study of TNBC patients (stages I-IV) diagnosed between 2006-2021 across two Mexican cancer centers.
- PD-L1 expression assessed centrally using the 22C3 pharmDx assay with Combined Positive Score (CPS) ≥1 considered positive.
- Exploration of associations between PD-L1 expression and clinicopathological features.
Main Results:
- PD-L1 positivity (CPS ≥1) was observed in 29.1% of 285 analyzed TNBC patients.
- PD-L1 positivity correlated with higher histological grades (91.3% vs. 78.5%) and high tumor-infiltrating lymphocytes (TILs ≥30%) (22.2% vs. 10.0%).
- Pre-treatment surgical specimens showed higher PD-L1 positivity (56.6%) compared to tumor biopsies (30.7%).
Conclusions:
- This study establishes PD-L1 positivity prevalence at 29.1% (CPS ≥1) in Mexican women with TNBC.
- PD-L1 positivity is linked to aggressive TNBC phenotypes, indicated by high TILs and histological grade.
- Clinicians must consider specimen type and the dynamic nature of PD-L1 expression for optimal metastatic TNBC treatment strategies.
