Serum β-2 microglobulin levels are associated with distant metastasis in patients with breast cancer

Serum β-2 microglobulin (β2-M) levels have been identified to be higher in patients with cancer than in healthy individuals. The aim of the present study was to evaluate the association between serum β2-M levels and clinicopathological characteristics of patients with breast cancer in a prospective cohort study, and to evaluate the effect of β2-M on cancer cell migration in vitro. Serum samples from 200 female patients with histologically confirmed invasive breast cancer were collected between 2017 and 2019. Their clinicopathological information was obtained and analyzed. The β2-M levels were identified to be associated with age, histologic subtype and metastatic status. When the diagnostic association of β2-M and metastatic status was analyzed, the area under the receiver operating characteristic curve was 0.78. Using a cut-off serum β2-M level of 1.9 µg/ml, the sensitivity for diagnosing metastatic status was 87.5%, the specificity was 65.0%, and the diagnostic odds ratio was 2.47. Upon age stratification, the association between the β2-M level and metastatic status was significant only in the group aged >55 years. In survival analysis, β2-M levels >1.9 µg/ml were associated with a poor survival outcome. In vitro, the MCF-7 breast cancer cell line exhibited increased cellular migration following treatment with 30 µg/ml β2-M. Serum β2-M may be a predictor of metastatic status in breast cancer.