Asian Multicenter Prospective Study in HER2 Positive Early Breast Cancer for Detecting MRD by ctDNA;HARMONY Study

This study will evaluate the relation between the detection rate of minimal residual disease(MRD) and recurrence in HER2-positive early breast cancer patients in Asian countries. Blood will be regularly collected to check the presence of ctDNA in HER2-positive breast cancer patients who have scheduled for neoadjuvant chemotherapy followed by surgery. Prognostic data is also collected on the same patients.

MRD is a small number of cancer cells left in the body during or after treatment. These cells have the potential to cause recurrence in cancer patients. MRD detection can help identify patients at increased risk of disease recurrence and guide treatment decisions. However, limited data are available on when ctDNA analysis should be done in the course of treatment, and what is the appropriate analysis method. This study will contribute to determining whether MRD detection using ctDNA is useful to predict the recurrence of HER2-positive early breast cancer patients. If this can be proven, it is expected that detection of MRD can use as a biomarker to assist in the de-/escalation of treatment strategies, therefore allowing to avoid overtreatment in patients at low risk, and to add more intensive treatment in patients at high risk. Moreover, studying with Asian countries, the results will become the basic data for approval of liquid biopsy.

• Overall survival (OS) [Time frame: The duration from the date of surgery until the date of death from any cause, up to 3 years.]
• Disease-free survival (DFS) [Time frame: The duration from the date of surgery until the date of first documented the DFS events, whichever comes first, up to 3 years.]