Cheng Ji, et al. - Cell-free DNA (cfDNA) is a marker for prognosis in patients with cancer. The purpose of the current study was to assess the prognostic value of cfDNA and cfDNA integrity (cfDI) in 268 patients with metastatic breast cancer. The cfDI was shown to be increased and the cfDNA was decreased after one cycle of chemotherapy. Cell-free DNA variables, with or without other biomarkers, are suitable prognostic markers for patients with metastatic breast cancer.