The article reviews the analytical validity and clinical potential of circulating tumor DNA (ctDNA) analysis in early breast cancer. While ctDNA analysis has gained popularity in metastatic breast cancer due to its ability to provide real-time tumor information, its application in early breast cancer has been limited by the relatively low sensitivity of available techniques. Advances in sequencing and bioinformatics, as well as the use of methylome profiles, have increased interest in ctDNA analysis for early breast cancer, from screening to treatment evaluation and minimal residual disease (MRD) detection. The article discusses the technical aspects of ctDNA detection, including tumor-agnostic and tumor-informed approaches, and reviews the analytical validity of different methods. It also examines the clinical applications of ctDNA in early breast cancer, such as screening, neoadjuvant therapy (NAT), adjuvant therapy, and MRD monitoring. The authors highlight the need for further validation and standardization of ctDNA assays to ensure their clinical utility. Prospective clinical trials are ongoing to evaluate the effectiveness of ctDNA in early breast cancer, and the article suggests that future research should focus on improving sensitivity and specificity, optimizing patient selection, and determining optimal testing timepoints.The article reviews the analytical validity and clinical potential of circulating tumor DNA (ctDNA) analysis in early breast cancer. While ctDNA analysis has gained popularity in metastatic breast cancer due to its ability to provide real-time tumor information, its application in early breast cancer has been limited by the relatively low sensitivity of available techniques. Advances in sequencing and bioinformatics, as well as the use of methylome profiles, have increased interest in ctDNA analysis for early breast cancer, from screening to treatment evaluation and minimal residual disease (MRD) detection. The article discusses the technical aspects of ctDNA detection, including tumor-agnostic and tumor-informed approaches, and reviews the analytical validity of different methods. It also examines the clinical applications of ctDNA in early breast cancer, such as screening, neoadjuvant therapy (NAT), adjuvant therapy, and MRD monitoring. The authors highlight the need for further validation and standardization of ctDNA assays to ensure their clinical utility. Prospective clinical trials are ongoing to evaluate the effectiveness of ctDNA in early breast cancer, and the article suggests that future research should focus on improving sensitivity and specificity, optimizing patient selection, and determining optimal testing timepoints.