• 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.