95MO Circulating tumor DNA (ctDNA) dynamics in patients (pts) receiving capecitabine (CAPE) for early-stage triple-negative breast cancer (eTNBC) with an incomplete response to neoadjuvant therapy (NAT)

Adjuvant CAPE is the standard-of-care (SoC) in eTNBC pts with incomplete response to anthracycline-based NAT. Presence of ctDNA following standard therapy early breast cancer associated poor relapse-free survival (RFS). Here, we evaluated rates detection before, during and after adjuvant CAPE. Pts residual disease NAT receiving for 6 months (+/- pembrolizumab) were enrolled 2 separate, prospective monitoring studies. Plasma samples (SignateraTM, bespoke mPCR-NGS assay) collected Association between burden (RCB) scores pathologic stage using chi square test. Correlation status outcomes was log-rank Median follow up 19.3 (range: 10.7-43.7). A total 29 a median age 43 years 33-78) included. RCB available 26 (I:10, II:12, III:4). positivity significantly higher III (p=0.0082) pN3 (p=0.0072). Detection 15% (3/20) prior 25% (7/28) completion Treatment did not result clearance any pts. Among 7 who ctDNA-positive, CAPE, (86%) subsequently experienced clinical relapse 3.85 0.6-11). ctDNA-positivity strongly inferior RFS (ctDNA-positive: 14% vs ctDNA-negative: 100%; p=0.0001). Only one pt died, 13 testing ctDNA-positive resulting an overall 97%. failed achieve this high-risk population. persistence on may prove useful as biomarker select patients novel agents trials.