Radiotherapy After Mastectomy for Breast Cancer Patients at Increased Risk of Local Recurrence

STUDY DESCRIPTION: This is a single-arm study to assess the feasibility, toxicity and cosmetic outcome of partial radiotherapy of the chest wall in breast cancer patients at increased risk of local relapse submitted to nipple-areola complex (NAC) sparing mastectomy and immediate implant-based reconstruction Inclusion criteria Histologically confirmed diagnosis of in situ ductal carcinoma (pTis) or invasive breast carcinoma (pT1 and pT2), submitted to NAC sparing mastectomy with prosthetic-based breast reconstruction (expander or prosthesis) and: Group A) Negative sentinel node dissection or axillary clearance (pN0) and all the following risk factors: Close (less than 1 mm) or positive (ink on tumor margin) surgical margin in a single breast quadrant Tumor diameter \>2 cm Age ≤50 years Group B) Positive sentinel dissection (pN1a) followed by axillary clearance (or primary axillary clearance) with only 1 positive node and any of the following risk factors: Close (less than 1 mm) or positive (ink on tumor margin) surgical margin in a single breast quadrant Age ≤50 years Tumor diameter \>2 cm Grade 3 histology Lymphovascular invasion HER-2 overexpression/amplification Triple negativity Treatment - Radioterapy The tumor bed is defined by the area at risk (skin and the pectoralis muscles) delineated by surgical clips and 3D-MRI reconstruction for a precise localization of the tumor excised. The clinical target volume (CTV) is defined as the tumor bed with a 1.5 cm margin limited by skin contour. A dose of 40 Gy is delivered in 16 fractions (2.5 Gy per fraction). For conventional post-mastectomy radiotherapy this moderately hypofractionated schedule is considered feasible and safe (31). Even more so, this schedule should be feasible and safe for a smaller irradiated volume as in the current protocol. Regional nodal irradiation is not considered at our Institution for patients fulfilling the entry criteria of the protocol. OUTCOME MEASURES Primary To assess feasibil