Evaluation of tumor-infiltrating lymphocytes, PD-L1, and PIK3CA mutations and association with prognosis in HER2-positive early stage breast cancer

Abstract

Background

Tumor-infiltrating lymphocytes (TILs) have predictive and prognostic potential in HER2-positive breast cancer (HER2+ BC). Programmed death-ligand 1 (PD-L1) is an immune checkpoint protein, with important roles in the tumor microenvironment, possibly in both tumor and immune cells (ICs), providing rationale for targeting with immune-checkpoint therapy. PIK3CA mutations are oncogenic, activating mutations, which are also of relevance in breast cancer. Herein, we investigate the frequency of TILs, PD-L1 and PIK3CA mutations, and whether these factors influence outcome, in early HER2+ BC.

Materials and methods

Stromal TILs (sTILs) and PD-L1 expressions were assessed using full tumor-sections and TMA, respectively, from 236 patients with HER2+ BC. TILs were assessed, according to a standardized method, as continuous measurement and according to three predefined categories: low (0–10%), intermediate (11–59%), and high (60–100%). PD-L1 immunohistochemistry (Ventana SP263) was evaluated and positivity defined as ≥1% expression in tumor and ICs. PIK3CA mutations (exons 9 and 20) were determined by pyrosequencing.

Results

Fourteen percent of patients had high sTILs and 25% had a PIK3CA mutation. PD-L1 expression was more frequent in ICs (68%) than tumor cells (24%). Patients with low sTILs had a significantly worse overall survival (multivariate: HR 2.80; 95% CI 1.36–5.78; p = .02).

Discussion

Patients with low sTILs had a significantly poorer survival, despite adequate treatment with adjuvant therapy.

Keywords:

• HER2-positive breast cancer
• tumor-infiltrating lymphocytes
• TILs
• PD-L1
• PIK3CA mutation

Acknowledgements

The authors would like to thank the laboratory at the Pathology Department, Zealand University Hospital for their work with TMA production. The PD-L1 assay was sponsored by Roche.

Author contributions

All authors contributed to the study conception and design. Data collection and analysis was performed by Frances Reznitsky. Statistical analysis was performed by Danish Breast Cancer Group’s secretariat. The first draft of the manuscript was written by Frances Reznitsky and all authors contributed on drafts of the manuscript. All authors read and approved the final manuscript.

Disclosure statement

The authors declare there are no conflicts of interest

Data availability statement

The data that support the findings of this study are available from the corresponding author, [FR], upon reasonable request.

Additional information

Funding

This study was funded by the Department of Pathology, Zealand University Hospital.