Efficacy and Safety of Prepectoral Prosthesis Immediate One-Stage Breast Reconstruction Versus Two-Stage Expander/Prosthesis Reconstruction in Postoperative Adjuvant Radiotherapy Breast Cancer Patients: A Prospective, Single-Center, Cohort Study

Inclusion criteria

• women aged 18 to 70；
• Newly diagnosed breast cancer patients showing no evidence of distant metastasis on clinical examination and diagnostic workup；
• adjuvant radiotherapy is required;
• Patients scheduled to undergo nipple-sparing mastectomy (NSM) or skin-sparing mastectomy (SSM) with immediate prepectoral implant-based reconstruction (via open, endoscopic, or robotic approach) require adjuvant radiotherapy AFTER permanent implant placement; OR Patients scheduled for NSM/SSM with two-stage tissue expander/implant reconstruction (with expander placement in either submuscular or prepectoral plane) receive radiotherapy WITH the tissue expander in situ, followed by exchange for permanent implant ≥6 months post-radiotherapy (expander position: submuscular/prepectoral acceptable; surgical approach: open/endoscopic/robotic acceptable);
• Patients are eligible regardless of whether mesh is used in the reconstruction surgery;
• Patients with severe breast ptosis are eligible;
• During the study observation period, lipofilling is permitted on the affected breast and symmetrization procedures on the contralateral breast in both cohorts;
• ECOG performance status 0-1;
• Patients receiving neoadjuvant chemotherapy (NACT) are eligible;
• Bilateral breast reconstruction is permitted;
• No smoking history OR smoking cessation ≥4 weeks prior to enrollment;
• Investigator-confirmed protocol compliance capability;
• Concurrent participation in other interventional/non-interventional trials is allowed if deemed non-interfering by the investigator;
• Voluntarily participate and sign the informed consent form after comprehensive understanding.

Exclusion criteria

• Stage IV (metastatic) breast cancer;
• No prior radiotherapy post-mastectomy;
• History of ipsilateral chest wall/axillary radiation therapy;
• Immunodeficiency, poorly controlled diabetes (HbA1c \>7%), or active tobacco use;
• Inflammatory breast cancer (cT4d);
• Autologous-based breast reconstruction or delayed reconstruction;
• Severe cardiopulmonary/hepatic/renal comorbidities contraindicating surgery/radiotherapy (ASA class ≥III);
• Psychiatric disorders precluding independent BREAST-Q completion;
• Pregnancy or lactation;
• Documented history of protocol non-adherence;
• Life-limiting comorbidities interfering with treatment OR investigator-determined ineligibility.