Breast cancer surgery that includes removal of lymph nodes from the armpit (axillary lymph node dissection) can disrupt normal lymphatic drainage and may lead to arm swelling, known as lymphedema. This condition can cause discomfort, limit arm function, and reduce quality of life. Patients with a higher body mass index and those who receive regional lymph node radiation are at particularly high risk.

This study aims to evaluate whether a preventive surgical technique, called axillary reconstruction using a pedicled lateral chest wall lymph-adipofascial flap, can reduce the risk of developing arm lymphedema after breast cancer surgery. During standard breast cancer surgery with axillary lymph node dissection, a small flap of tissue containing fat, fascia, and lymphatic tissue from the lateral chest wall is rotated into the axillary area to fill the surgical space and support lymphatic drainage.

This is a prospective, single-arm Phase II clinical study. Participants will be followed for up to 24 months after surgery to assess the occurrence of arm lymphedema, changes in arm volume and bioimpedance measurements, quality of life, and surgery-related complications. The results of this study may help determine whether this simple and widely applicable technique can safely reduce the risk of lymphedema in high-risk breast cancer patients.

Breast cancer-related arm lymphedema is a common and long-term complication following breast cancer surgery that includes axillary lymph node dissection. Disruption of lymphatic drainage pathways in the axilla can lead to chronic arm swelling, discomfort, recurrent infections, and impaired quality of life. The risk of lymphedema is particularly high in patients with elevated body mass index and those who require regional lymph node radiation therapy.

Current preventive surgical approaches mainly focus on immediate lymphatic reconstruction using lymphatic-venous anastomosis. Although this technique may reduce early postoperative lymphedema in selected patients, its long-term effectiveness remains uncertain. In addition, the procedure requires microsurgical expertise and specialized equipment, limiting its widespread implementation. A substantial proportion of patients are also not suitable candidates due to the absence of identifiable lymphatic vessels for anastomosis.

An alternative preventive strategy is axillary reconstruction using vascularized lymph-adipofascial tissue. The lateral chest wall contains abundant adipose tissue, deep fascia, and lymphatic networks supplied by reliable perforating vessels. A pedicled lateral chest wall lymph-adipofascial flap can be harvested without microsurgical anastomosis and rotated into the axillary defect created after lymph node dissection. This approach aims to reduce postoperative dead space, modulate fibrosis, and provide a biologically favorable environment that may support lymphatic drainage and tissue remodeling.

This study is a prospective, single-arm Phase II clinical trial designed to evaluate the efficacy and safety of axillary reconstruction using a pedicled lateral chest wall lymph-adipofascial flap in breast cancer patients at high risk for lymphedema. Eligible participants will undergo standard breast cancer surgery with axillary lymph node dissection, followed by immediate axillary reconstruction using the pedicled flap. The procedure adds minimal operative time and does not require microsurgical techniques.

Participants will be followed for up to 24 months after surgery. The study will assess the incidence of postoperative arm lymphedema, longitudinal changes in objective arm measurements, patient-reported quality of life, oncologic outcomes, and surgery-related complications. By focusing on a high-risk population, this study aims to clarify whether this simple and widely applicable surgical technique can safely reduce the burden of lymphedema and improve postoperative recovery after breast cancer surgery.

Inclusion Criteria:

1. Female patients aged 18 to 75 years;
2. Histologically confirmed invasive breast cancer;
3. Pathologically confirmed axillary lymph node metastasis requiring axillary lymph node dissection;
4. Body mass index (BMI) ≥ 25 kg/m²;
5. Planned to receive postoperative regional lymph node radiation therapy;
6. Ability to understand the study procedures and provide written informed consent;
7. Willingness and ability to comply with study follow-up and assessments.

Exclusion Criteria:

1. Previous surgery involving the ipsilateral axilla;
2. Previous radiation therapy to the ipsilateral axilla;
3. Evidence of distant metastatic breast cancer;
4. Bilateral breast cancer, or a history of contralateral breast cancer surgery;
5. Severe hepatic or renal dysfunction, or severe cardiac insufficiency;
6. Inability to read or understand Chinese sufficiently to complete study questionnaires and assessments;
7. Pregnancy;
8. Any condition or circumstance that, in the investigator's judgment, may interfere with study compliance or follow-up.

Individual participant data (IPD) will not be shared. The data collected will be used solely for the purposes of this study and related scientific publications.