The future of blood-based biomarkers for the early detection of breast cancer.

Breast cancer (BC) is the most frequently diagnosed cancer and the most common cause of cancer-related mortality among women worldwide. Despite the extensive use of mammography as the gold standard for BC screening, the occurrences of false-positive and false-negative mammograms, as well as overdiagnosis, remain a concern in breast oncology. Thus, there is a need to identify reliable biomarkers from an easily accessible source that could generate cost-effective assays feasible for routine screening. Blood-based biomarkers may offer an alternative non-invasive strategy to improve cancer screening. Although none of the currently used blood-based biomarkers are sensitive enough for the early detection of BC, a plethora of significant findings pertaining to the development of screening tools using blood-based biomarkers have emerged in recent years. Promising candidate biomarkers such as proteins, autoantibodies, miRNAs, nucleic acid methylation, metabolites and lipids have shown great potential for detecting BC, including detection at the pre-invasive and early stages of the disease. Nevertheless, blood-based biomarkers for BC screening are still at the early phases of development, and various clinical and preclinical issues need to be addressed before these biomarkers can be used clinically. This review summarises the latest discoveries for harnessing blood-based biomarkers as novel BC screening tools, as well as discusses the limitations and challenges that need to be overcome before the translation of their use from the bench to the bedside.