Radiotherapy of breast cancer: 2025 update

Adjuvant radiotherapy is a key component in the management of breast cancer. After breast-conserving surgery for invasive carcinoma, adjuvant irradiation is systematically recommended regardless of patient characteristics, as it reduces the risk of local recurrence and improves survival. A boost to the tumour bed is indicated for patients under 50years of age. Partial breast irradiation may be considered as an alternative to whole-breast irradiation, but only in carefully selected and fully informed patients. For ductal carcinoma in situ, postoperative irradiation is also systematically recommended after lumpectomy. After mastectomy, chest wall irradiation is indicated for pT4 tumours or in the presence of nodal involvement; it may be individualized for pT3 or pN1 tumours. When neoadjuvant chemotherapy precedes mastectomy, radiotherapy is recommended if the initial tumour was classified as T3-T4 or if clinical or radiological nodal involvement was present prior to chemotherapy, indication which can be questioned in the absence of lymph node involvement on the surgical specimen, depending on the tumour subtype. Axillary irradiation is indicated based on nodal dissection findings and may be considered in cases of sentinel node involvement without dissection. Supraclavicular and infraclavicular nodal irradiation is recommended in cases of histologically proven axillary involvement, while internal mammary node irradiation should be evaluated individually, based on the benefit/risk balance, particularly due to potential cardiac toxicity. Moderate hypofractionation is now the standard for whole-breast irradiation after lumpectomy, regardless of patient profile, due to its equivalent efficacy compared to conventional fractionation. It is also feasible for chest wall irradiation. Furthermore, recent randomized trials have shown that moderate hypofractionation can be applied to nodal irradiation without increased toxicity. For whole-breast irradiation alone, ultra hypofractionation (26Gy delivered in five fractions) has demonstrated non-inferiority to moderate hypofractionation. Target volume delineation for the breast with or without boost, chest wall, and nodal areas relies on clinical, surgical, pathological, and initial imaging data. Various techniques are available (three-dimensional conformal radiotherapy or intensity-modulated radiotherapy); the selected approach should optimize target coverage while respecting organ-at-risk constraints. Respiratory gating should be offered when it helps reduce exposure to organs at risk, particularly the heart. Adjuvant chemotherapy is generally not delivered concurrently with radiotherapy. Hormone therapy may be initiated before, during, or after irradiation.