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

• •1. women aged 18 to 70；
• •2. Newly diagnosed breast cancer patients showing no evidence of distant metastasis on clinical examination and diagnostic workup；
• •3. adjuvant radiotherapy is required;
• •4. 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);
• •5. Patients are eligible regardless of whether mesh is used in the reconstruction surgery;
• •6. Patients with severe breast ptosis are eligible;
• •7. During the study observation period, lipofilling is permitted on the affected breast and symmetrization procedures on the contralateral breast in both cohorts;
• •8. ECOG performance status 0-1;
• •9. Patients receiving neoadjuvant chemotherapy (NACT) are eligible;
• •10. Bilateral breast reconstruction is permitted;
• •11. No smoking history OR smoking cessation ≥4 weeks prior to enrollment;
• •12. Investigator-confirmed protocol compliance capability;
• •13. Concurrent participation in other interventional/non-interventional trials is allowed if deemed non-interfering by the investigator;
• •14. Voluntarily participate and sign the informed consent form after comprehensive understanding.