Inclusion Criteria:

1. Written informed consent prior to any specific study procedure.

2. Patients with willingness and ability to comply with study procedures.

3. Patients (women and men) ≥18 years of age.

4. Patients with a first diagnosis of the UICC (Union for International Cancer Control) stage I-III primary invasive BC whose tumors are of any of the following subtypes:

   • Luminal: Hormonal Receptor(HR)-positive and HER2-negative.
   • HER2-positive: HER2-positive regardless of the HR status.
   • Triple negative: Hormonal Receptor(HR)-negative and HER2-negative. HR and HER2 status should be based on local laboratory determination following the criteria of the American Society of Clinical Oncology/College of American Pathologists (ASCO/CAP) international guidelines in effect at the time of testing.

5. Patients that are scheduled to receive NAT as determined by the treating physician according to standard clinical practice.

6. Archival Formalin-Fixed, Paraffin-Embedded (FFPE) sample of the primary tumor must be available to analyze tumor-informed ctDNA assays.

Exclusion Criteria:

1. Patients with stage IV BC.
2. Patients with previous anti-cancer treatment for the current BC.
3. Patients with diagnosis of any other invasive malignancy in the 5 prior years, unless the malignancy has been treated with curative intent and is considered at low risk of recurrence, with no evidence of active disease at study entry.
4. Patients with a diagnosis of bilateral or multifocal breast tumors with different HR or HER2 status.
5. Patients with any severe acute or chronic medical or psychiatric condition or laboratory abnormality that may interfere with the interpretation of study results and, in the judgment of the investigator, would make the patient inappropriate for entry into this study.
6. Patients who are concurrently enrolled in clinical trials.
7. Females who are pregnant or breastfeeding.