Abstract: Objective　To investigate the correlation between tumor infiltrating myeloid-derived suppressor cells (MDSCs) and peripheral blood leukocytes in patients with breast cancer, and its effect on the relapse-free survival (RFS). Methods　The clinical data and the proportion of tumor infiltrating MDSCs of 32 patients with breast cancer who underwent radical surgery in Tianjin Cancer Hospital were collected. The relationship between MDSCs and clinicopathological features was analyzed. The correlation between MDSCs and peripheral blood leukocytes was observed by Spearman correlation analysis. The patients were divided into the high MDSCs group (≥4.4%, n=16) and the low MDSCs group (＜4.4%, n=16) according to the median MDSCs. The difference of RFS between the two groups was analyzed. Results　The proportion of tumor infiltrating MDSCs was higher in patients with stage Ⅲ than that of patients with stageⅠ-Ⅱ (P＜0.05). The proportion of MDSCs infiltrated by tumor was positively correlated with peripheral blood monocyte count (rs=0.405) and monocyte to lymphocyte ratio (MLR) (rs=0.408, P＜0.05). Overall analysis results showed that RFS values of the high and low MDSCs groups were [(102.7±9.1) months and (107.9±8.3) months], and there was no significant difference between the two groups (Log-rank χ2=1.166, P＞0.05). Stratified analysis showed that in 17 cases without lymph node metastasis RFS was significantly shorter in the high MDSC group [(97.4±31.9) months] than that of the low MDSCs group [(117.8±15.9) months, Log-rank χ2=5.402, P＜0.05]. Conclusion　The proportion of MDSCs infiltrating in breast cancer is positively correlated with peripheral blood monocyte count and MLR. Patients without lymph node metastasis have worse RFS in the high MDSCs group.

Key words: breast neoplasms, monocytes, myeloid derived suppressor cells, recurrence free survival time