Applications of ctDNA testing to monitor and detect residual disease in breast cancer

In recent years, circulating tumor DNA (ctDNA) has emerged as a promising method for detection of minimal or molecular residual disease (MRD) among patients with breast cancer. In this narrative review, we provide a summary of currently available studies assessing use of ctDNA in detection of MRD in patients after completion of curative therapy. Additionally, we discuss limitations of present studies, future considerations, and an overview of ongoing trials evaluating the clinical utility of MRD-directed therapy interventions. While the clinical utility of MRD-directed therapy guidance remains under investigation, collective data from studies overwhelmingly confirm the prognostic value of ctDNA status across various stages and subtypes of breast cancer. Results from ongoing clinical trials in the coming years will provide more clarity on the overall clinical benefit of MRD-directed interventions for breast cancer patients.