Prevalence of Programmed Death-Ligand 1 Positivity Using SP142 in Patients With Advanced Stage Triple-Negative Breast Cancer in Malaysia: A Cross-Sectional Study.

Purpose: Triple-negative breast cancer (TNBC) is a subtype of breast cancer known for its poor prognosis and the absence of viable targets for standard receptor-based therapies. Several studies have suggested that targeting programmed death-ligand 1 (PD-L1) in tumors that express this biomarker, either on tumor cells and/or in the tumor inflammatory infiltrate, may be beneficial in some patients. This study aimed to assess the overall prevalence of PD-L1 positivity using the SP142 antibody clone in patients with advanced TNBC in Malaysia.

Methods: This was a multicenter, cross-sectional prevalence study on PD-L1 positivity among patients with advanced-stage TNBC in Malaysia. Patients were identified using medical records and were enrolled in the study if they met the inclusion criteria. PD-L1 evaluation was performed using archived formalin-fixed paraffin-embedded tissue specimens. Demographic and clinical data were also obtained and summarized using descriptive statistics. The association of these parameters with PD-L1 positivity was assessed using chi-square and logistic regression analysis.

Results: Three medical centers provided 138 complete cases for analysis. Of these 138 cases, 52 (37.7%; 95% confidence interval, 29.6%-46.3%) showed positive PD-L1 expression, defined as immune cell PD-L1 expression ≥ 1%. In a univariate analysis, stage III of the disease and tumor samples from resected specimens were significantly associated with a positive PD-L1 status. However, further assessment using a multivariate model revealed that only resected tumor samples remained significantly associated with PD-L1 positivity after controlling for disease staging.

Conclusion: The prevalence of PD-L1 positivity among patients with stage III or IV TNBC was 37.7%. A significant association was noted between PD-L1 positivity and the tumor tissue obtained from resected specimens. Although the mechanism and clinical significance of this association remain unclear, this finding indicates a possible disparity in the PD-L1 status of samples obtained using surgical resection or biopsy.