This study is the first prospective randomized study assessing the patient-reported outcomes and safety outcomes between preoperative and postmastectomy radiotherapy in locally advanced breast cancer patients with immediate reconstruction of deep inferior epigastric perforator(DIEP) flap. Radiotherapy before mastectomy and autologous free-flap breast reconstruction can avoid adverse radiation effects on healthy donor tissues and delays to adjuvant radiotherapy. We aimed to explore the feasibility of preoperative radiotherapy followed by DIEP flap reconstruction in patients with breast cancer requiring mastectomy.

Inclusion Criteria:

• Patients with histological proven invasive breast cancer;
• Clinical T0-3, T4b and N0-3a disease who require neoadjuvant chemotherapy;
• No distant metastasis;
• Adjuvant radiotherapy and who are suitable for DIEP flap reconstruction at the time of mastectomy.

Exclusion Criteria:

• Patients enrolled in other clinical trial which may as influence the outcome;
• Patients received neoadjuvant therapy without radiotherapy indications；
• Disease progression during neoadjuvant chemotherapy；
• Patients of pregnancy or lactation；
• Previous history of diabetes；
• Previous history of heavy smoking.