Association of clinical outcomes in metastatic breast cancer patients with circulating tumour cell and circulating cell-free DNA.

•Circulating tumour cell (CTC) or cell-free DNA (ccfDNA) associated with metastatic breast cancer (MBC) patient survivals.•Prognostic values of CTC and ccfDNA largely non-overlapping.•CTC and ccfDNA jointly associated with patient survival, especially overall survival.•Potential combined use of CTC and ccfDNA as liquid biopsy in MBC management.