Brief Summary This observational study will follow patients who undergo DIEP flap breast reconstruction to better understand a common surgical challenge called ischemia-reperfusion (I/R) injury. I/R injury can happen when a flap has a period without blood flow (ischemia) and then blood flow returns (reperfusion). This process may trigger inflammation and oxidative stress and is associated with fat necrosis or partial flap loss.

1. What is being studied

1. The investigators will measure inflammation and oxidative stress markers in blood (for example, interleukin-6 [IL-6]) from before surgery through the first 72 hours after surgery.
2. These data will help map the normal and abnormal patterns of recovery after surgery and may inform future approaches to monitoring and protecting flap tissue.
3. No experimental drug or device is given to participants in this study. Separate animal studies are developing a near-infrared imaging and antioxidant nanomaterial (Mn/QD-SAC); this is not used in participants here.

2. Who can take part

1. Women aged 18-70 scheduled for immediate DIEP flap breast reconstruction after breast cancer surgery.
2. Key exclusions include severe heart, liver, or kidney disease; significant clotting problems; active infection or autoimmune disease; long-term use of immunosuppressants/anti-inflammatory drugs; pregnancy or breastfeeding; or other reasons judged by the research team.

3. What will happen if you join

1. After providing informed consent, participants will have blood drawn at five time points: pre-operative baseline (within 24 hours before surgery) and at 0, 6, 24, and 72 hours after surgery (about 10 mL each time; total ~50 mL).
2. Blood will be processed and stored under secure conditions and tested for inflammation and oxidative stress markers.
3. The investigators will also record routine clinical information from the medical record (such as age, BMI, surgery duration, ischemia time, and clinical assessments of flap outcomes and complications).
4. Participation does not change the participant's clinical care before, during, or after surgery.

4. Risks and benefits

1. Risks are those of standard blood draws: brief pain, bruising, bleeding, dizziness, and rare infection.
2. There is no direct medical benefit to participants. Results may help improve understanding and future care for patients undergoing flap reconstruction.

5. Privacy and data protection

1. Samples and data will be coded without names. Identifying information is stored separately with restricted access.
2. Research results are not routinely added to the medical record or returned to participants unless a finding has clear, actionable clinical significance and is approved by the ethics committee.

6. Time commitment and costs

1. All blood draws occur during the routine hospital stay. There is no additional follow-up required after discharge.
2. There is no cost to participate.

7. Voluntary participation Joining the study is voluntary. Participants may withdraw at any time without affecting their medical care.

Inclusion Criteria:

1. Female, 18-70 years old.
2. Clinically diagnosed with breast cancer and scheduled for immediate DIEP free-flap breast reconstruction after mastectomy.
3. Conscious and able to understand and voluntarily sign written informed consent.

Exclusion Criteria:

1. Severe cardiac, hepatic, or renal dysfunction or severe coagulopathy (e.g., NYHA class III-IV, Child-Pugh class C, eGFR <30 mL/min/1.73 m²).
2. Preoperative active infection, autoimmune disease, or long-term use of immunosuppressants/anti-inflammatory drugs (e.g., corticosteroids).
3. Pregnant or breastfeeding.
4. Prior ipsilateral breast surgery or radiotherapy that may affect local blood circulation assessment.
5. Any condition deemed unsuitable by the investigator (e.g., poor compliance).

Hospitalized adult women (18-70 years) with breast cancer at Hubei Cancer Hospital undergoing mastectomy with immediate DIEP free-flap breast reconstruction. Approximately 30 consecutive eligible patients able to provide written informed consent will be enrolled. Exclusions include severe cardiac/hepatic/renal dysfunction or severe coagulopathy, preoperative active infection, autoimmune disease or chronic immunosuppressive/anti-inflammatory therapy (e.g., corticosteroids), pregnancy or breastfeeding, and prior ipsilateral breast surgery or radiotherapy. This is an observational perioperative biomarker cohort; no investigational agents or devices are administered.

IPD will not be shared due to patient privacy and ethical considerations, absence of consent for data sharing, institutional/regulatory restrictions, and limited resources for secure de-identification and data hosting. Aggregate results will be available in publications or upon request.