This is a cohort, single-center, prospective study that seeks to analyze the circulating tumor DNA (ctDNA) in patients diagnosed with breast cancer, who will undergo neoadjuvant treatment.

Breast cancer is a major public health problem, being the most common cancer in women worldwide. Breast cancer can be diagnosed through multiple tests, including an imaging and tissue biopsy. However, accurate assessment and prediction of the response is a major challenge. Circulating tumor DNA (ctDNA) has shown promise in the detection of breast cancer and clinical and cancer outcomes.

This study aims to evaluate a possible correlations between ctDNA levels with the pathological complete response and detection of residual disease after neoadjuvant therapy in patients with breast cancer.

In order to start ctDNA surveillance, patients will be asked to participate in blood draws, every 15 days, during neoadjuvant standard institutional treatment and allow study staff to review medical records.

Inclusion Criteria:

• Information to the patient and signed informed consent;
• Locally advanced breast cancer that is a candidate for neoadjuvant therapy;
• Histological diagnosis of localized invasive breast carcinoma, confirmed by the pathologist, with or without expression of hormone receptors, and/or with the presence of HER-2.

Exclusion Criteria:

• Metastatic breast cancer (Stage IV);
• Additional invasive malignant disease;
• Known psychiatric or substance abuse disorders that may interfere with cooperation with study requirements;
• Presents any organic condition that makes it impossible to carry out chemotherapy treatment;
• Pregnant or lactating women
• Received previous treatment for breast cancer.

Patients diagnosed with breast cancer who are considered possible candidates for neoadjuvant chemotherapy

The findings will be shared and discussed with all investigators in the study. A study manuscript, having received contributions from all authors, will be submitted for publication in scientific circles.