Primary Objective:

1) To examine the impact of Circulating tumor DNA (ctDNA) (expressed as mean tumor molecules per ml) on treatment decision making in patients with early stage breast cancer after neoadjuvant therapy and surgery

Secondary Objectives:

1. Understand ctNDA kinetics in the neoadjuvant and adjuvant setting
2. To identify any associations between clinical staging and measurable ctDNA

To determine whether early detection of Circulating tumor DNA (ctDNA) after neoadjuvant systemic therapy help tailor adjuvant therapy and reduce risk of relapse in patients who are at increased risk of recurrence. Studies have shown the presence of ctDNA is associated with increased risk of relapse, it is unclear how adjuvant therapy and its effect of ctDNA impacts the risk of relapse. There is very limited data on the role of ctDNA monitoring and response to neoadjuvant/adjuvant systemic therapy in patients with human epidermal growth factor receptor 2 (HER2 ) positive breast cancer.

Natera, Inc. (NASDAQ: NTRA) has developed a minimal residual disease (MRD) assay that sequences tumor tissue to identify a unique signature of tumor mutations, then customizes a personalized PCR assay for each participant, targeting the top 16 clonal mutations found in the tumor (Signatera™). Signatera is intended to detect and quantify how much cancer is left in the body, to improve prognosis and help optimize treatment decisions, based on the tissue-informed testing of mutations.

If the ctDNA blood test is positive, change in treatment can be made after discussion with the participant and treating provider. If the decision is for observation (Observation defined for TNBC: No adjuvant chemotherapy. Participants may complete checkpoint inhibitor from neoadjuvant setting. HER2 positive breast cancer: complete 12 months of anti-HER2 therapy, which was initiated in neoadjuvant setting), participants in the observation arm, will be monitored for ct-DNA re-emergence and systemic therapy can be added at the time of ctDNA re-emergence. If the decision is made to institute systemic therapy based on the ctDNA detection, participants will be monitored with ctDNA at 60days, 3 months, 6 months, 9 months, 12 months, 18months and 24months from surgery. If ctDNA is negative, there will be no change in therapy and participants can continue on observation arm (Observation defined for TNBC: No adjuvant chemotherapy. Participants may complete checkpoint inhibitor from neoadjuvant setting. HER2 positive breast cancer: complete 12 months of anti-HER2 therapy, which was initiated in neoadjuvant setting). Participants in the observation arm will be monitored for ct-DNA re-emergence and systemic therapy can be added at the time of ctDNA re-emergence.

The treating oncologist will complete a questionnaire to determine how ctDNA impacts treatment decisions in the adjuvant setting once the results from the fourteen day ctDNA is available and at the time of ctDNA re-emergence. Participants will complete participant questionnaire at 3 months, 6months,12months and 24 months post-operatively. Participants will be followed up for five years.

Inclusion Criteria:

• Participants with a diagnosis of clinical Stage II-III triple negative and/or HER2 positive breast cancer
• Age ≥ 18 years
• Estimated life expectancy of at least twelve months
• Participant must be eligible for neoadjuvant systemic therapy per treating physician
• Eastern Cooperative Oncology Group (ECOG) performance status ≤ 2
• Able to provide signed and dated informed consent form
• Must have ctDNA at the time of screening to be eligible for the study
• Participants enrolled on other systemic therapy trials may be eligible to participate in the study after discussion with principal investigator
• Be willing to present for medical exams and blood draws as scheduled per protocol

Exclusion Criteria:

• Evidence of metastatic breast cancer
• Any other concurrent malignancy
• Prior malignancies (except non-melanoma skin cancers, and the following in situ cancers: bladder, gastric, colon, endometrial, cervical/dysplasia, melanoma, or breast) unless a complete remission was achieved at least one year prior to study entry
• Participant is pregnant
• Serious concomitant systemic disorder that would compromise the safety of the participant or compromise the participant's ability to complete the study, at the discretion of the investigator
• Bone marrow transplant or other organ transplant recipient
• History of psychiatric illness or social situations that would limit compliance with study requirements
• Has a history or current evidence of any condition, therapy, or laboratory abnormality that might confound the results of the trial, interfere with the subject's participation for the full duration of the trial, or is not in the best interest of the subject to participate, in the opinion of the treating investigator

The plan to share IPD will be determined by the PI and updated accordingly.