Hypofractionated vs. Conventionally Fractionated Postmastectomy Radiotherapy After Implant-Based Reconstruction

Inclusion Criteria:

• Female patients aged ≥ 18 years.
• Pathologically confirmed unilateral primary invasive breast cancer.
• Underwent skin-sparing (SSM) or nipple-sparing mastectomy (NSM) with axillary staging (sentinel lymph node biopsy or axillary lymph node dissection).
• Underwent 1-stage (direct-to-implant) or 2-stage (tissue expander) reconstruction, or implant combined with autologous tissue, with prepectoral or subpectoral placement.
• Received standard neoadjuvant or adjuvant systemic therapy (chemotherapy, endocrine, anti-HER2, or targeted therapy) according to guidelines or clinical trial protocols.
• Definite indication for post-mastectomy chest wall ± regional nodal irradiation according to guidelines (typically c/pT1-3 N0-3 M0).
• Interval of at least 6 weeks between reconstruction surgery and the initiation of radiotherapy.
• ECOG performance status 0-1.
• Prior non-breast malignancy permitted if disease-free for > 5 years with low recurrence risk; prior cervical or colon carcinoma in situ, melanoma in situ, basal cell carcinoma, or squamous cell skin carcinoma permitted regardless of disease-free interval.
• Estimated life expectancy ≥ 10 years.
• Written informed consent provided.

Exclusion Criteria:

• Pregnant or lactating patients.
• Prior history of breast cancer.
• Bilateral breast cancer.
• Prior radiotherapy to the ipsilateral chest wall or regional lymph node areas.
• T4 disease (including, but not limited to, inflammatory breast cancer, regardless of response to neoadjuvant systemic therapy).
• Non-breast malignancy within the past 5 years (except cervical or colon carcinoma in situ, melanoma in situ, basal cell carcinoma, or squamous cell skin carcinoma).
• Severe non-malignant comorbidities (e.g., cardiovascular disease, pulmonary disease, systemic lupus erythematosus, or scleroderma) precluding radiotherapy tolerance or follow-up compliance.