Prognostic significance of peripheral myeloid-derived suppressor cells in advanced breast cancer

The exact roles of myeloid-derived suppressor cells (MDSCs) and regulatory T cells in the peripheral blood of individuals with advanced breast cancer undergoing chemotherapy remain unclear. This study aimed to assess peripheral blood immune-related markers, including MDSCs, in patients with advanced breast cancer treated with chemotherapy, and to examine the relationship between these immune cells and clinical outcomes. We also examined the relationship between MDSCs and peripheral blood biomarkers, including the absolute lymphocyte count and neutrophil-to-lymphocyte ratio. Seventy-three women who were treated with chemotherapy for advanced breast cancer were evaluated. Blood samples from patients at baseline and after cycle 1 treatment were subjected to flow cytometry. Individuals with a lower baseline level of MDSCs demonstrated a significantly longer progression-free survival (PFS) and a tendency for enhanced overall survival (OS) compared with those with a higher level of MDSCs. The baseline level of MDSCs was a significant independent prognostic factor for PFS. Patients with a low proportion of MDSCs after cycle 1 had significantly better PFS and OS than their counterparts. The group of patients with a low proportion of MDSCs at baseline and after cycle 1 showed significantly better PFS and OS than the other groups. Patients with a low absolute lymphocyte count, an elevated neutrophil-to-lymphocyte ratio, and a reduced lymphocyte-to-monocyte ratio exhibited significantly higher MDSC levels. The level of MDSCs may serve as a prognostic indicator for individuals with advanced breast cancer. Peripheral blood biomarkers may reflect the proportion of circulating MDSCs.