To investigate the expression of micro RNA-21 (miR-21) and micro RNA-17-5p (miR-17-5p) in the plasma of patients with breast cancer and their diagnostic values.

Eighty-six patients with breast cancer diagnosed in Chengdu Seventh People’s Hospital from June 2017 to March 2018 were selected as the breast cancer group, and 45 healthy women were selected as the control group. Real-time quantitative polymerase chain reaction (qRT-PCR) was used to detect the expression of miR-21 and miR-17-5p in plasma exosomes of two groups. According to the results of qRT-PCR, breast cancer patients were divided into miR-17-5p high-expression group and miR-17-5p low-expression group, miR-21 high-expression group and miR-21 low-expression group, and the relationship between them with clinicopathological parameters of breast cancer patients was analyzed. The diagnostic values of plasma exosomes miR-21 and miR-17-5p in breast cancer were analyzed by receiver operating characteristic curve (ROC).

The expression of plasma exosome miR-17-5p in breast cancer group was significantly lower than that in control group (P<0.05), and the expression of plasma exosomemiR-21 was significantly higher (P<0.05). The area under curve (AUC) of detection of miR-17-5p alone was 0.677, the sensitivity was 58.14%, the specificity was 75.56%, and the truncation value was 0.72; the AUC of detection of miR-21 alone was 0.694, the sensitivity was 59.30%, the specificity was 77.78%, and the truncation value was 1.68; the sensitivity, specificity and accuracy of combined detection were 96.51%, 95.56% and 96.18% respectively; the sensitivity, specificity and accuracy of combined detection of breast cancer were significantly higher than those of single detection (P<0.05). The expression levels ofmiR-17-5p and miR-21in plasma exosomes were correlated with TNM stage, differentiation degree, lymph nodemetastasis, cerbB-2 and Ki-67 (P<0.05).

Low expression of miR-17-5p and high expression of miR-21 in plasma exosome can be used as potential biomarkers for the diagnosis of breast cancer.