Comparison of the Safety and Aesthetic Outcomes of a Novel Endoscopic-Assisted Breast-Conserving Surgery (SRRSHzb-EABCS) With Those of Conventional Breast-Conserving Surgery

Study Design: This is a multicenter, open-label, prospective, randomized controlled trial led by Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, with multiple participating centers in China.

Randomization: Eligible female patients with breast cancer who meet the inclusion criteria and sign informed consent are randomly assigned in a 1:1 ratio to the experimental group (SRRSHzb-EABCS) or the control group (conventional open breast-conserving surgery) one day before surgery. The randomization sequence is generated centrally by computer (ResMan system) with stratification by center.

Experimental intervention (SRRSHzb-EABCS): The procedure uses a gasless "expansion-traction" endoscopic system with two custom-built instruments (a skin flap dissector and a V-shaped retractor) and a metal wire-based system for tumor localization and margin control (Lu Y, et al. Laparoscopic, Endoscopic and Robotic Surgery, 2026; doi: 10.1016/j.lers.2026.08.004). Under general anesthesia, the patient is positioned supine with the affected arm abducted at 60-75 degrees and the ipsilateral shoulder elevated. A single 3.0-4.5 cm curvilinear incision is made in the axilla, limited to the triangular area bounded by the lateral border of the pectoralis major and the anterior border of the latissimus dorsi. Preoperative ultrasound delineates the tumor margin; a circular outline 1.5-2.0 cm from the tumor edge is marked on the skin and divided into eight equal segments to define cutting points, with four marking points positioned circumferentially between alternating pairs of cutting points. Sentinel lymph node biopsy or axillary lymph node dissection is performed through the axillary incision, and the retromammary space is then dissected endoscopically toward the tumor, with the upper blade of the V-shaped retractor used in traction mode to maintain a stable working space. Four circumferential U-shaped cutting wires (0.3 mm metal wire advanced via a 20G angiocatheter, with limbs insulated by sheaths) are placed percutaneously along the resection boundary, and two insulating marking wires are placed in a cross configuration posterior to the tumor within the retromammary space as visual guides; additional wires are used for large or irregularly shaped tumors. The subcutaneous flap is dissected with the custom-built skin flap dissector, and the V-shaped retractor is then repositioned in expansion mode with both blades spread apart to maintain the superficial working space. The ends of each U-shaped wire are connected to an electrocautery pencil; under endoscopic vision, the wire is lifted vertically and activated, cutting precisely along the pre-determined resection plane ("hot-wire" cutting). The remaining parenchymal bridges are divided using standard laparoscopic instruments guided by the marking wires. The specimen is removed en bloc through the axillary incision, and all margins are assessed by intraoperative frozen section; positive margins undergo re-excision through the same incision, and repeatedly positive margins lead to mastectomy. The defect is reconstructed with a pedicled glandular flap using volume displacement oncoplastic technique, titanium clips are placed in the tumor bed, and the cavity is drained and closed.

Control intervention (conventional open breast-conserving surgery): Performed according to the Chinese Anti-Cancer Association guidelines for breast-conserving therapy, generally with separate breast and axillary incisions. The resection includes the tumor with surrounding breast tissue, with oncoplastic volume displacement or replacement techniques when needed. Specimen margins are marked and assessed (margin inking and/or intraoperative frozen section and imprint cytology), 4-6 titanium clips are placed in the tumor bed. If a margin is positive on intraoperative or postoperative pathology, local re-excision of the margin is performed, and if margins remain repeatedly positive, mastectomy is performed.

Axillary management in both groups: sentinel lymph node biopsy for clinically node-negative patients, with axillary lymph node dissection according to biopsy results; clinically node-positive patients undergo axillary lymph node dissection directly.

Pathology and adjuvant therapy: All specimens are examined by pathologists according to the Chinese Anti-Cancer Association breast cancer guidelines, and all margin results are recorded in the case report form. Postoperative adjuvant therapy is determined by the treating physician according to current guidelines and recorded.

Follow-up: Participants are followed at 1 month and 18 months after surgery to record complications and complete BREAST-Q assessments. Long-term follow-up for local recurrence, disease-free survival, and overall survival continues for 5 years after surgery.

Sample size: Based on pilot data from the lead center, the positive margin rate of SRRSHzb-EABCS was 25% compared with 15% for conventional open surgery. Using a non-inferiority margin of 10%, a one-sided alpha of 0.025, and 80% power, and accounting for a 5% dropout rate, 211 participants are required per arm (422 in total).

Safety monitoring: All intraoperative and postoperative complications (including wound infection, postoperative bleeding, seroma, and flap necrosis), their management, and outcomes are recorded in the case report form.