Discordance of PD-L1 status between primary and metastatic breast cancer : A systematic review and meta-analysis

• INTRODUCTION: Programmed cell death ligand 1 (PD-L1) expression is predictive for benefit from immunotherapy in several human malignancies including triple negative breast cancer. Lower positivity rates but a larger relative benefit from atezolizumab has been implied when PD-L1 status is assessed at metastatic sites. We aimed to study the discordance of PD-L1 expression between primary tumor and metastasis in breast cancer due to its potential clinical utility.METHODS: Cochrane Library, Embase, Medline and Web of science were searched for studies reporting on PD-L1 expression in primary and metastatic breast cancer, followed by data extraction. Outcomes included pooled PD-L1 positivity rates in tumor cells, immune cells or both in primary tumor and metastasis, PD-L1 discordance between matched primary tumors and metastasis and direction of discordance.RESULTS: Of 2552 identified entries following de-duplication, 20 studies fulfilled the predefined inclusion criteria. Pooled PD-L1 positivity rate was higher in primary tumors compared to metastasis when assessed in immune cells (51.2% vs 37.1% p < 0.001) and tumor/immune cells (30.1% vs 14.6% p < 0.001), but not in tumor cells (18.7% vs 17.8% p = 0.65). PD-L1 positivity was lowest when assessed in bone metastases (12%) and highest in lymph nodes (60%). Discordance between primary tumors and metastasis was bidirectional, with higher pooled discordance rates when PD-L1 expression was assessed in immune compared to tumor cells (39.5% vs 13.6%, p < 0.001).CONCLUSION: The observed considerable discordance between PD-L1 status in primary and metastatic breast cancer emphasizes the importance of appropriate tissue sampling when selecting patients for immunotherapy.

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin -- Cancer och onkologi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine -- Cancer and Oncology (hsv//eng)

Nyckelord

Breast cancer

Discordance

Immunotherapy

Metastasis

PD-L1

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