The main objective of the study is to validate the DAT technique in patients with Her2-positive breast cancer who have more than two positive axillary lymph nodes at diagnosis. After receiving adequate oncological treatment and axillary assessment by ultrasound for complete radiological response, DAT and Berg level I and II lymphadenectomy will be performed to assess false negatives and positives, as well as their sensitivity and specificity.

This study aims to determine whether axillary treatment can be further de-escalated in patients with HER2-positive breast cancer, as this group has shown good responses to certain targeted therapies. It focuses on reducing the need for extensive axillary surgery (known as axillary lymphadenectomy or AL), which can cause complications, by using a less invasive procedure called Targeted Axillary Dissection (TAD). This method combines the removal of sentinel lymph nodes and previously marked nodes, allowing for an assessment of treatment response without needing to remove all lymph nodes. Currently, this method is used in patients diagnosed with axillary disease involving fewer than two axillary nodes.

Main Objective:

To evaluate whether axillary lymphadenectomy can be avoided in HER2-positive breast cancer patients with more than two affected axillary nodes who respond well to chemotherapy before surgery.

Secondary Objectives:

Analyze the oncological treatment response in these patients. Determine how many affected nodes respond to the treatment. Evaluate whether the number of affected nodes at diagnosis limits the possibility of performing TAD.

Compare methods for locating the affected nodes. Verify the concordance between marked nodes and sentinel nodes.

Methodology:

This is a multicenter, prospective descriptive study. Women with HER2-positive breast cancer who receive chemotherapy before surgery will be included. Those who show a good axillary response will be offered the TAD procedure, followed by lymphadenectomy, to assess the sensitivity, specificity, false negatives, and true positives of the technique. Clinical and radiological data will be collected to analyze outcomes and complications.

Significance:

The TAD procedure has already allowed this hospital to reduce extensive axillary surgeries by 30%, preventing associated complications. This study seeks to confirm whether this approach is safe and effective in a specific group of HER2-positive breast cancer patients with more than two affected nodes at diagnosis. If successful, it could lead to a change in how these patients are treated, reducing risks and improving their quality of life.

Inclusion Criteria:

• ECOG 0-1 (physical condition: able to walk and live a normal life)
• Patients with early-stage breast cancer (BC) with histopathological diagnosis of HER2+ and axillary involvement.

Patients with either positive or negative hormonal receptor expression will be included.

• Patients must have marked the pathological axillary lymph node.

• Any number of affected or suspicious lymph nodes at diagnosis is allowed.

• Patients will receive appropriate neoadjuvant treatment based on a combination of chemotherapy and anti-HER2 therapy.

  • After neoadjuvant treatment and prior to surgery, radiological response will be assessed.

• No relevant comorbidities, adequate liver and kidney function, and no contraindications to receive neoadjuvant treatment followed by surgery and radiotherapy.

Exclusion Criteria:

• Patients with inoperable breast cancer.
• Patients with a diagnosis of inflammatory breast cancer.
• Patients without a diagnostic biopsy of the suspicious lymph node or the presence of axillary conglomerate.

The study population consists of patients with HER2+ breast cancer, with more than two affected lymph nodes at diagnosis, who receive chemotherapy. These patients have been marked at diagnosis and show a good response after neoadjuvant treatment

The data will be protected in the patient's medical record, although the patient is informed about the study and will sign a consent form. It is uncertain whether it is ethical to share the individual data.