Personalized mutation tracking in circulating-tumor DNA predicts recurrence in patients with high-risk early breast cancer.

The clinical utilization of circulating tumor DNA (ctDNA) in breast cancer (BC) management is not well-defined. In this prospective study, 168 patients with early-stage BC were recruited, serial blood samples were collected before and after surgery. Tumor-informed ctDNA testing was performed, which sequenced tumors for 95 genes followed by bespoke mPCR to track 1-9 mutations in the plasma. ctDNA was detected before surgery in 14.6%, 40.0%, 83.8%, and 80.0% of HR+ low-risk, HR+ high-risk, HR-HER2+ and HR-HER2- patients, respectively. Pre-operative ctDNA positivity was significantly associated with decreased disease-free survival (DFS) (adjusted HR = 3.09, 95% CI 2.65-80.0, p = 0.001). After a median 26.6-month follow-up, 11 patients relapsed, and ctDNA at landmark time point 2-4 weeks after surgery was detected in 50.0% (5/10) of cases. Landmark ctDNA clearance was associated with significantly longer DFS (p = 0.0009) and positive ctDNA persistence after adjuvant therapy occurred in 36.4% (4/11) of stage-III patients. During surveillance, ctDNA detection had 90.9% sensitivity and 98.8% specificity to predict recurrence, and median lead time of 9.7 months. Patients with detected ctDNA had shorter DFS than those with undetectable ctDNA (adjusted HR = 207.05, 95% CI 41.38- > 1000, p = 0.001). Therefore, ctDNA status both before and after surgery could help stratify recurrence risk for BC patients.