CD3, CD4, and CD8 staining, but not PD-L1, are positively correlated with overall survival in Asian breast cancer

Given the fundamental importance of T lymphocytes in the effectiveness of cancer immunotherapy, and potentially in the response to chemotherapy and radiotherapy, immune cell markers have been evaluated as predictive and prognostic biomarkers, with conflicting results in the different subtypes of breast cancer and in different studies. In this study, we report the association of T lymphocyte markers with overall survival in a cross-sectional cohort of Asian breast cancer patients. Formalin-fixed, paraffin-embedded tumour samples from 576 breast cancer patients from a Malaysian hospital were stained with CD3, CD4, CD8 and PD-L1 antibodies, and area-based positive staining was quantified from digitized whole slide images. At a median follow up of 68 months, we report that CD3, CD4 and CD8 scores, but not PDL1 scores, were associated with overall survival, with the strongest associations seen in triple-negative breast cancer (TNBC). CD3, CD4, and CD8 scores were also compared to genomic and transcriptomic data from previous studies, and found to have a negative association with copy number aberrations, but no association with tumour mutational burden or neoantigen load. Taken together, T lymphocyte markers may be associated with good prognosis in Asian breast cancer patients.