Elevated serum soluble programmed death ligand 1 (sPD-L1) level correlate with clinical characteristics in breast cancer patients: A study at Hospital Universiti Sains Malaysia

•Most clinically used serological biomarkers for post-treatment monitoring are not the same ones used during IHC tissue staining for treatment stratification.•Serum sPD-L1 expression in Malaysian breast cancer patients is significantly elevated compared to healthy volunteers.•Serum sPD-L1 can be used as liquid biopsy using the same patented antibodies applied in companion diagnostics IHC PD-L1. Elevated serum levels of soluble PD-L1 (sPD-L1) have been reported in many cancers; however, there is limited data of sPD-L1 in breast cancer, especially those representing Asian (Malay) women. The purpose of this study was to evaluate sPD-L1 serum levels and analyze its correlation with clinical characteristics in breast cancer patients at Hospital Universiti Sains Malaysia (HUSM). Blood specimens were obtained from 92 malignant, 16 benign breast cancer patients and 23 healthy controls. The serum concentrations of sPD-L1 were assessed by enzyme-linked immunosorbent assay (ELISA). The median serum sPD-L1 concentration of malignant and benign breast cancer patients was significantly elevated compared to the healthy cohorts (12.50 ng/mL vs 13.97 ng/mL vs 8.75 ng/mL, p