This is a national multicenter, prospective, cohort study. The study aims to compare surgical safety (e.g., surgical complication rates), surgery-related indicators (e.g., operation time, number of operations, surgery-related costs, contralateral breast adjustment operation rates), aesthetic outcomes (e.g., BREAST-Q scores, Harris scores, SCAR-Q scores, Ueda scores and QLQ-BR45 scores), and divorce rate between patients undergoing delayed endoscopic direct-to-implant breast reconstruction via an axillary approach and those undergoing the two-stage expander-to-implant breast reconstruction following simple mastectomy.

Breast cancer is one of the most prevalent malignant tumors among women, with comprehensive treatment primarily centered around surgery being the mainstay approach. Mastectomy accounts for 88.8% of primary breast cancer surgeries, yet the rate of immediate breast reconstruction is only about 10.7%, resulting in the majority of patients losing their breasts at the time of initial surgery and suffering from long-term suboptimal psychosocial health, with divorce rates reaching as high as 40%. With the improvement in breast cancer treatment outcomes, an increasing number of women hope to improve postoperative breast morphology and alleviate psychological trauma through breast reconstruction. Traditional reconstruction methods include autologous tissue reconstruction and prosthetic reconstruction. The former involves significant trauma and a high incidence of complications, while the latter often requires a two-stage approach due to insufficient skin tissue, involving initial placement of a tissue expander followed by replacement with a prosthetic implant, which increases the number of surgeries and the risk of complications.

To address this issue, our team has developed a novel delayed endoscopic direct-to-implant breast reconstruction technique via an axillary incision approach with insufflation, which requires only a single surgery, significantly reducing surgical time, trauma, and costs, as well as the incidence of complications. Postoperatively, there are no fresh incisions on the breast, resulting in a more natural appearance and softer feel. This study aims to compare this technique with the traditional two-stage approach, exploring postoperative complications, aesthetic outcomes, quality of life, cost-effectiveness, and surgical-related indicators. To comprehensively evaluate its clinical benefits, large-scale multicenter studies are required to provide evidence-based medical evidence and optimize surgical strategies.

Therefore, this national multicenter, prospective, cohort study will compare surgical safety (e.g., surgical complication rates), surgery-related indicators (e.g., operation time, number of operations, surgery-related costs, contralateral breast adjustment operation rates), aesthetic outcomes (e.g., BREAST-Q scores, Harris scores, SCAR-Q scores, Ueda scores and QLQ-BR45 scores), and divorce rate between patients undergoing delayed endoscopic direct-to-implant breast reconstruction via an axillary approach and those undergoing the two-stage expander-to-implant breast reconstruction following simple mastectomy.

Inclusion Criteria:

• Female patients aged 18-70 years (inclusive) who have undergone simple mastectomy for breast cancer;
• At least 1 year after simple mastectomy or 6 months after completion of radiotherapy, with good local skin viability and skin laxity;
• Voluntary provision of informed consent.

Exclusion Criteria:

• Local/regional recurrence or uncontrolled distant metastasis detected upon re-examination (clinical, imaging, or pathological evidence);
• Pectoralis major muscle was resected during the initial surgery;
• Preoperative severe comorbidities with poor general condition, rendering the patient unable to tolerate surgery;
• Immunodeficiency;
• Long-term smoking history or poorly controlled diabetes mellitus;
• Currently participating in other clinical trials that may affect the results of this study.

Qualified researchers can request access to anonymized individual patient-level data via the request portal. All IPD requests should be emailed to Dr. Zhenggui Du, the general project leader, and will be evaluated by Dr. Du and the head of the collaborating organization to decide whether to approve.

After publication of relevant research outputs, such as academic papers and books

When a request has been approved, the investigator will provide access to the de-identified individual patient-level data in the data management platform (Electronic Data Capture, EDC). A signed Data Sharing Agreement (non-negotiable contract for data accessors) must be in place before accessing the requested information. Additionally, all users will need to accept the terms and conditions of the data management platform to gain access.