This is a prospective and observational study, aiming to determine the detection rate and change of CtDNA in blood samples of cancer patients before, during and after neoadjuvant treatment.

• Determine the rate of ctDNA positivity at the time before treatment,
• Determine the rate of ctDNA positivity at the time during treatment,
• Determine the rate of ctDNA positivity at the time after neoadjuvant therapy, whether there is a change in ctDNA expression of the study population during treatment.

And aiming to investigate the relationship between ctDNA expression and MRI imaging with pCR response in neo-adjuvant therapy:

• Correlation between ctDNA detection and pCR response. Determine the percentage of Positive Prediction Value - PPV, Negative Prediction Value - NPV of ctDNA,
• Correlation between MRI imaging and pCR response. Determination of PPV, NPV of MRI
• Combination of ctDNA detection and MRI imaging in the prognosis of pCR. Determination of PPV, NPV ratio of ctDNA combined with MRI.

This is a prospective and observational study recruiting Female participants aged 18 and older, who are diagnosed with stage II-III HER+/Triple Negative Breast cancer and indicated for neoadjuvant chemotherapy at University Medical Center HCMC, had FFPE sample at the time of diagnosis and operation. This study is conducted at the Medical Genetics Institute (MGI), and MRCCC Siloam Hospitals Semanggi (Indonesia) in collaboration with the University Medical Center HCMC.

Eligible neoadjuvant chemotherapy (NAC) / treatment regimen for the study:

• AC-T (Doxorubicin, Cyclophosphamid - Taxane).
• AC-TH (Doxorubicin, Cyclophosphamid - Taxane - Trastuzumab).
• TCH (Docetaxel - Carboplatin - Trastuzumab).
• TCHP (Docetaxel - Carboplatin - Trastuzumab - Pertuzumab).

Patients are allowed to change protocol if required clinically.

The potential and voluntary participants, satisfy all the inclusion/exclusion criteria will be recruited into this study.

At enrollment, each participant will answer to the pre-designed questionnaires of demographic information, medical history.

At routine visits, the participants' clinical information and routine para-clinical results such as breast ultrasound or MRI or CT scan, chest x-ray, mamography, bone or PET-CT scan, CA 15-3 will be collected by Physicians.

Participant in this study will have samples collected the following period of time.

• At enrollment (Pre-NAC, at diagnosis): 10ml of peripheral blood for ctDNA analysis and 6-8 sections of formalin-fixed paraffin-embedded (FFPE) tumor samples collected as biopsy before treatment.
• During NAC, 10ml of peripheral blood will be collected for ctDNA analysis and Ultrasound scan of neck, breast, abdomen and pelvis; chest x-ray, CA15-3; CT Scan of the neck, abdomen and pelvis (if any) will be also collected.
• Post-NAC, 10ml of peripheral blood will be collected for ctDNA analysis and Ultrasound scan of neck, breast, abdomen and pelvis; chest x-ray, CA15-3; CT Scan of the neck, abdomen and pelvis, PET-CT scan (if any) will be also collected to compare to treatment respondence between ctDNA and imaging groups.
• After surgery, 6-8 sections of formalin-fixed paraffin-embedded (FFPE) tumor samples collected.

The study end date of a participant is estimated 1 year since enrollment date.

Inclusion Criteria:

• Female,18 years old and older,
• Are diagnosed with stage II-III HER2+/Triple Negative breast cancer and indicated for neoadjuvant chemotherapy,
• FFPE sample is available at the time of diagnosis and operation,
• Are voluntary to participate in the study.

Exclusion Criteria:

• Recurrent breast cancer,
• Other cancer metastasis to the breast,
• Have been or are being treated for cancer,
• Patients did not agree to participate in the studies.

The study population will include female, from 18 years old or above, who are diagnosed with stage II-III HER2+/Triple Negative breast cancer and indicated for neoadjuvant chemotherapy. Eligible participants will meet all of the inclusion and exclusion criteria to be recruited into this study at University Medical Center HCMC, MRCCC Siloam Hospitals Semanggi (Indonesia).

Anonymised data of this study may be requested for publication by journals. Sharing anonymised data with suitable study will be decided by the sponsor, PIs and the authority agency where the data was collected. No identifiable information will be share with any other person/organization than authorized in the study.

Feb 2026

GS_ZNAB_ctDNA for Breast cancer