Correlation between the expression of CD24 on circulating tumor cells and prognosis in breast cancer

Objective: To investigate the expression of tumor stem cell marker CD24 in peripheral blood circulating tumor cells (CTCs) of breast cancer and the value of CTCs in predicting the prognosis of breast cancer patients. Methods: Clinical data of 102 breast cancer patients from January 2015 to December 2019 were retrospectively collected. CTC test results, CD24 test results, tumor size, tumor stage, pathological type, molecular type, lymph node metastasis, survival time, and survival status of patients were collected. The correlation between the expression of CD24 in peripheral blood CTCs of breast cancer and the survival time of patients was analyzed. Results: Epithelial-CTCs were closely related to estrogen receptor (ER) expression (P = 0.036) and TNM stage (P = 0.018). Mixed epithelial/mesenchymal-CTCs were closely related to lymph node metastasis in breast cancer patients (P = 0.026). There was no obvious correlation between mesenchymal-CTCs and clinical characteristics (P > 0.05). The positive expression rate of CD24 in CTCs was 58.82% (60/102). The number of CD24-positive CTCs was closely related to TNM stage (P = 0.002), lymph node metastasis (P = 0.020), and tumor size (P = 0.025). The cumulative survival rate of patients with CD24-positive CTCs > 1.5/5 ml (73%) was significantly worse than that of patients with CD24-positive CTCs <= 1.5/5 ml (88%) (P < 0.05). There was no significant difference in the cumulative survival rate be-tween patients with mixed-CTCs > 2.5/5 ml (72%) and patients with mixed-CTCs <= 2.5/5 ml (87%) (P = 0.336). The cumulative survival rate of patients with CD24-positive mixed-CTCs > 0.5/5 ml (72%) was significantly lower than that of patients with CD24-positive mixed-CTCs <= 0.5/5 ml (92%) (P < 0.05). Conclusion: The positive expression of CD24 in CTC is closely related to TNM stage, lymph node metastasis, and tumor size in breast cancer patients. The positive expression of CD24 in CTCs, especially in mixed-CTCs, may be one of the prognostic indicators for patients with early and intermediate stage breast cancer.