This is a Phase II, interventional, prospective, single-arm, multi-center study that will enroll patients with stage II/III triple negative breast cancer (TNBC) who have residual cancer burden (RCB) II/III after conventional neoadjuvant chemo-immunotherapy followed by surgery. Technological advances in ctDNA assays have improved both the sensitivity and reliability of molecular residual disease (MRD) detection to enable real-time measurement with clinical-grade assays.

The primary objective of this study will be to evaluate ctDNA-based MRD status in high-risk, early-stage TNBC patients by defining the proportion of TNBC patients with MRD-only recurrence (ctDNA positive without radiographically measurable recurrence) during post-surgery surveillance. The secondary objectives will evaluate the safety, preliminary efficacy, and survival outcomes of using Dato-DXd in participants with MRD-only TNBC.

Dato-DXd is an investigational antibody-drug conjugate (monoclonal antibody specific for TROP2 and a topoisomerase I (Topo-1) inhibitor) that has demonstrated promising efficacy in TNBC patients with a manageable safety profile.

Despite treatment advances, patients with II/III triple negative breast cancer (TNBC) residual disease post-neoadjuvant therapy, particularly patients with higher residual cancer burden (RCB II/III), remain at high risk for developing recurrence. Furthermore, early detection of relapse risk, when the residual disease burden is micrometastatic (defined here as undetectable by standard cross-sectional imaging), provides a chance for disease eradication whereas macrometastatic disease (i.e., detectable on standard cross-sectional imaging) is generally considered to be non-curable.

There are no standard of care (SOC) surveillance strategies for early detection of micrometastatic disease in high-risk TNBC beyond clinical monitoring. Detecting molecular residual disease (MRD) is a promising approach to identifying patients at increased risk of recurrence after definitive therapy, who may benefit from the escalation of their treatment and remain potentially curable with effective systemic therapy.

Inclusion Criteria:

Written informed consent was obtained to participate in the study, and HIPAA authorization for the release of personal health information.

• Participant is willing and able to comply with study procedures based on the judgment of the investigator.
• Age ≥ 18 years at the time of consent.
• Histological confirmation of TNBC defined by ER/PR <10%, HER2 0-1+ by IHC or 2+ by IHC and fluorescence in situ hybridization (FISH) negative.
• Stage II/III TNBC treated with neoadjuvant systemic therapy AND have residual disease defined as RCB II/III at time of surgery.
• Baseline staging scans at the discretion of the treating physician and demonstrate no evidence of metastatic disease.
• The participant must have archival diagnostic tissue and/or surgical resection tissue Available.
• Participants are willing and able to comply with study procedures based on the judgment of the investigator.

Exclusion Criteria:

• Participants are pregnant or breastfeeding.