Longitudinal dynamics of circulating tumor DNA for treatment monitoring in patients with breast cancer recurrence.

The prevalence and dynamics of circulating tumor DNA (ctDNA) in patients with breast cancer recurrence or de novo metastatic cancer were examined in a retrospective analysis of a prospective observational cohort. Twenty-three recurrent/metastatic breast cancer cases (8 locoregional, 15 distant metastasis) were enrolled, and sequential plasma samples were obtained. Anchor mutations were selected from the target sequencing of each patient's primary and/or metastatic tumor.